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general description the MAX2038 8-channel variable-gain amplifier (vga) and programmable octal mixer array is designed for high linearity, high dynamic range, and low noise per- formance targeting ultrasound imaging and doppler applications. each amplifier features differential inputs and outputs and a total gain range of 42db (typ). in addition, the vgas offer very low output-referred noise performance suitable for interfacing with 12-bit adcs. the MAX2038 vga is optimized for less than ?.25db absolute gain error to ensure minimal channel-to-chan- nel ultrasound beamforming focus error. the device? differential outputs are designed to directly drive ultra- sound adcs through an external passive anti-aliasing filter. a switchable clamp is also provided at each amplifier? output to limit the output signals, thereby preventing adc overdrive or saturation. dynamic performance of the device is optimized to reduce distortion to support second-harmonic imaging. the device achieves a second-harmonic distortion specification of -70dbc at v out = 1.5v p-p and f in = 5mhz and an ultrasound-specific*, two-tone, third-order intermodulation distortion specification of -52dbc at v out = 1.5v p-p and f in = 5mhz. the MAX2038 also integrates an octal quadrature mixer array and programmable lo phase generators for a complete cw beamforming solution. the lo phase selection for each channel can be programmed using a digital serial interface and a single high-frequency clock or the los for each complex mixer pair can be directly driven using separate 4 x lo clocks. the serial interface is designed to allow multiple devices to be easily daisy chained to minimize program interface wiring. the lo phase dividers can be programmed to allow 4, 8, or 16 quadrature phases. the input path of each cw mixer consists of a selectable lowpass filter for optimal cwd noise performance. the outputs of the mixers are summed into i and q differential current outputs. the mixers and lo generators are designed to have excep- tionally low noise performance of -155dbc/hz at 1khz offset from a 1.25mhz carrier. the MAX2038 operates from a +5.0v power supply, consuming only 120mw/channel in vga mode and 269mw/channel in normal power cw mode. a low- power cw mode is also available and consumes only 226mw/channel. the device is available in a lead-free 100-pin tqfp package (14mm x 14mm x 1mm) with an exposed pad. electrical performance is guaranteed over a 0 c to +70 c temperature range. applications ultrasound imaging sonar features 8-channel configuration high integration for ultrasound imaging applications pin compatible with the max2037 ultrasound vga vga features maximum gain, gain range, and output-referred noise optimized for interfacing with 12-bit adcs maximum gain of 29.5db total gain range of 42db 22nv/ hz ultra-low output-referred noise at 5mhz 0.25db absolute gain error 120mw consumption per channel switchable output vga clamp eliminating adc overdrive fully differential vga outputs for direct adc drive variable gain range achieves 42db dynamic range -70dbc hd2 at v out = 1.5v p-p and f in = 5mhz two-tone ultrasound-specific* imd3 of -52dbc at v out = 1.5v p-p and f in = 5mhz cw doppler mixer features low mixer noise of -155dbc/hz at 1khz offset from 1.25mhz carrier serial-programmable lo phase generator for 4, 8, 16 lo quadrature phase resolution optional individual channel 4 x f lo lo input drive capability 269mw power consumption per channel (normal power mode) and 226mw power consumption per channel (low-power mode) cwd implementation is fully compliant with all patents related to ultrasound imaging techniques MAX2038 ultrasound vga integrated with cw octal mixer ________________________________________________________________ maxim integrated products 1 ordering information 19-4375; rev 0; 1/09 evaluation kit available for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. + denotes a lead(pb)-free/rohs-compliant package. d = dry packing. t = tape and reel. * ep = exposed pad. part temp range pin-package MAX2038ccq+d 0 c to +70 c 100 tqfp-ep* MAX2038ccq+td 0 c to +70 c 100 tqfp-ep* pin configuration appears at end of data sheet. * see the ultrasound-specific imd3 specification in the applications information section.
MAX2038 ultrasound vga integrated with cw octal mixer 2 _______________________________________________________________________________________ absolute maximum ratings dc electrical characteristicsvga mode ( typical application circuit , figure 7. v cc = v ref = 4.75v to 5.25v, v cm = (3/5)v ref , t a = 0 c to +70 c, v gnd = 0, low_pwr = 0, m4_en = 0, cw_filter = 0 or 1, tmode = 0, pd = 0, cw_vg = 1, cw_m1 = 0, cw_m2 = 0, no rf signals applied, capacitance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , cw mixer outputs pulled up to +11v through four separate ?.1% 115 resistors, all cw channels programmed off. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) (note 2) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v cc , v ref to gnd .................................................-0.3v to +5.5v any other pins to gnd...............................-0.3v to (v cc + 0.3v) cw mixer output voltage to gnd (cw_iout+, cw_iout-, cw_qout+, cw_qout-) ................................................13v vga differential input voltage (vgin_+, vgin_-)............8.0v p-p analog gain control differential input voltage (vg_ctl+, vg_ctl-) ..................................................8.0v p-p cw mixer differential input voltage (cwin_+, cwin_-).......................................................8.0v p-p cw mixer lvds lo differential input voltage..................8.0v p-p continuous power dissipation (t a = +70?) 100-pin tqfp (derated 45.5mw/? above +70?)...3636.4mw operating temperature range...............................0? to +70? junction temperature ......................................................+150? jc (note 1) .....................................................................+2?/w ja (note 1) ...................................................................+22?/w storage temperature range .............................-40? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol condtions min typ max units vga mode supply voltage range v cc 4.75 5 5.25 v v cc external reference v ref (note 3) 4.75 5 5.25 v pd = 0 204 231 total power-supply current refers to v cc supply current plus v ref current pd =1 27 33 ma v cc supply current i vcc 192 216 ma v ref current i ref 12 15 ma current consumption per amplifier channel refers to v cc supply current 24 27 ma minimum gain +2 differential analog control voltage range maximum gain -2 v p-p differential analog control common-mode voltage v cm 2.85 3 3.15 v analog control input source/sink current 4.5 5 ma logic inputs cmos input high voltage v ih 2.3 v cmos input low voltage v il 0.8 v note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial .
MAX2038 ultrasound vga integrated with cw octal mixer _______________________________________________________________________________________ 3 dc electrical characteristicscw mixer mode ( typical application circuit , figure 7. v cc = v ref = 4.75v to 5.25v, t a = 0 c to +70 c, v gnd = 0, low_pwr = 0, m4_en = 0, cw_filter = 0 or 1, tmode = 0, pd = 0, cw_vg = 0, cw_m1 = 0, cw_m2 = 0, no rf signals applied, capacitance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , cw mixer outputs pulled up to +11v through four separate ?.1% 115 resistors. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) (note 2) parameter symbol condtions min typ max units cw mixer mode current in full-power mode 5v v cc supply i cc_fp refer s to v c c sup p l y cur r ent ( al l 8 channel s) 245 265 ma current in full-power mode 11v v mix supply i mix _ fp refer s to v m ix sup p l y cur r ent ( al l 8 channel s) 106 120 ma current in full-power mode 5v v ref supply i ref_fp refer s to v re f sup p l y cur r ent ( al l 8 channel s) 17 21 ma power dissipation in full-power mode p diss_fp total power dissipation (all 8 channels including both 5v (v cc and v ref ) and 11v mixer pullup supply power dissipation in the device) (note 4) 2.15 2.41 w current in low-power mode 5v v cc supply i cc_lp low _p wr = 1; r efer s to v c c sup p l y cur r ent ( al l 8 channel s) 245 265 ma current in low-power mode 11v v mix supply i mix_lp low _p wr = 1; r efer s to v m ix sup p l y cur r ent ( al l 8 channel s) 53 60 ma current in low-power mode 5v v ref supply i ref_lp low _p wr = 1; r efer s to v r e f sup p l y cur r ent ( al l 8 channel s) 17 21 ma power dissipation in low-power mode p diss_lp low_pwr = 1; total power dissipation (all 8 channels including both 5v (v cc and v ref ) and 11v mixer pullup supply power dissipation in the device) (note 4) 1.81 2.06 w mixer lvds lo input common- mode voltage modes 1 and 2 (note 5) 1.25 ?.2 v lvds lo differential input voltage modes 1 and 2 200 700 mv p-p lvds lo input common-mode current per pin 150 200 ? lvds lo differential input resistance modes 1 and 2 (note 6) 30 k mixer if common-mode output current common-mode current in each of the differential mixer outputs (note 7) 3.25 3.75 ma data output high voltage dout voltage when terminated in din (daisy chain) (note 8) 4.5 v data output low voltage dout voltage when terminated in din (daisy chain) (note 8) 0.5 v
MAX2038 ultrasound vga integrated with cw octal mixer 4 _______________________________________________________________________________________ ac electrical characteristicsvga mode ( typical application circuit , figure 7. v cc = v ref = 4.75v to 5.25v, v cm = (3/5)v ref , t a = 0 c to +70 c, v gnd = 0, low_pwr = 0, m4_en = 0, cw_filter = 1, tmode = 0, pd = 0, cw_vg = 1, cw_m1 = 0, cw_m2 = 0, vg_clamp_mode = 1, f rf = f lo /16 = 5mhz, capacitance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10 pf, r l = 1k , cw mixer outputs pulled up to +11v through four separate ?.1% 115 resistors, differential mixer inputs are driven from a low impedance source. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units mode select response time cw_vg set from logic 1 to 0 or from 0 to 1 (note 9) 2s vga mode differential output capacitance is 10pf, capacitance to gnd at each single-ended output is 60pf, r l = 1k 18 full-scale bandwidth f -1.3db v out = 1.5v p-p , 1.3db bandwidth, gain = 10db no capacitive load r l = 1k 29 mhz small-signal bandwidth f -1.3db v out = 1.5mv p-p , 3db bandwidth, gain = 10db 30 mhz differential input resistance r in 170 200 230 input effective capacitance c in f rf = 10mhz, each input to ground 15 pf differential output resistance r out 100 maximum gain +29.5 db minimum gain -12.5 db gain range 42 db absolute gain error t a = +25 c, full gain range 0% to 100%, v ref = 5v ?.25 ?.5 db vga gain response time 40db gain change to within 1db final value 1 ? input-referred noise vg_ctl set for maximum gain, no input signal 2 nv/ hz no input signal 22 output-referred noise vg_ctl set for +10db of gain v out = 1.5v p-p , 1khz offset 55 nv/ hz v g_c lam p _m od e = 1, v g_c tl set for + 10d b of g ai n, f r f = 5m h z, v ou t = 1.5v p - p -70 second harmonic hd2 v g_c lam p _m od e = 1, v g _c tl set for + 10d b of g ai n, f r f = 10m h z, v ou t = 1.5v p - p -55 -65 dbc third-order intermodulation distortion imd3 v g_c lt set for + 10d b of g ai n, f rf1 = 5m h z, f r f2 = 5.01mhz, v out = 1.5v p-p , v ref = 5v (note 3) -40 -52 dbc channel-to-channel crosstalk v out = 1v p-p differential, f r f = 10mhz, vg_ctl set for +10db of gain -80 db maximum output voltage at clampon vg_clamp_mode = 0, vg_ctl set for +20db of gain, 350mv p-p differential input 2.4 v p-p d i ffer enti al
MAX2038 ultrasound vga integrated with cw octal mixer _______________________________________________________________________________________ 5 ac electrical characteristicscw mixer mode ( typical application circuit , figure 7. v cc = v ref = 4.75v to 5.25v, t a = 0 c to +70 c, v gnd = 0, low_pwr = 0, m4_en = 0, cw_filter = 1, tmode = 0, pd = 0, cw_vg = 0, cw_m1 = 0, cw_m2 = 0, vg_clamp_mode = 1, f rf = f lo /16 = 5mhz, capaci- tance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , cw mixer outputs pulled up to +11v through four separate ?.1% 115 resistors, differential mixer inputs are driven from a low imped- ance source. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units maximum output voltage at clampoff vg_clamp_mode = 1, vg_ctl set for +20db of gain, 350mv p-p differential input 2.8 v p-p d i ffer enti al cw mixer mode mixer rf frequency range 0.9 7.6 mhz mixer lo frequency range 1 7.5 mhz mixer if frequency range 100 khz maximum input voltage range 1.8 v p-p d i ffer enti al cw_filter = 0 633 differential input resistance cw_filter = 1 1440 m od e 3, f rf = f lo /4 = 1.25m h z, m easur ed at a 1kh z offset fr eq uency; cl utter tone at 0.9v p - p d i ffer enti al m easur ed at the m i xer i np ut 6 input-referred noise voltage m od e 3, rf ter m i nated i nto 50 ; f l o /4 = 1.25m h z, m easur ed at 1kh z offset 4.6 nv/ hz third-order intermodulation distortion imd3 m od e 1, f rf 1 = 5m h z at 0.9v p - p d i ffer enti al i np ut, d op p l er tone f rf 2 = 5.01m h z at 25d bc fr om cl utter tone, f lo /16 = 5m h z ( n ote 10) -50 dbc m i xer o utp ut v ol tag e c om p l i ance (note 11) 4.75 12 v channel-to-channel phase matching measured under zero beat conditions, f rf = 5mhz, f lo /16 = 5mhz (note 12) ?.0 degrees channel-to-channel gain matching measured under zero beat conditions, f rf = 5mhz, f lo /16 = 5mhz (note 12) ? db cw_filter = 1 2.8 transconductance (note 13) cw filter = 0 f rf = 1.1mhz, 1v p - p d i ffer enti al , f lo /16 = 1mhz 2.8 ms
MAX2038 ultrasound vga integrated with cw octal mixer 6 _______________________________________________________________________________________ ac electrical characteristicscw mixer mode (continued) ( typical application circuit , figure 7. v cc = v ref = 4.75v to 5.25v, t a = 0 c to +70 c, v gnd = 0, low_pwr = 0, m4_en = 0, cw_filter = 1, tmode = 0, pd = 0, cw_vg = 0, cw_m1 = 0, cw_m2 = 0, vg_clamp_mode = 1, f rf = f lo /16 = 5mhz, capaci- tance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , cw mixer outputs pulled up to +11v through four separate ?.1% 115 resistors, differential mixer inputs are driven from a low imped- ance source. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units serial shift register serial shift register programming rate 10 mhz minimum data set-up time t dsu 30 ns minimum data hold time t hld 2ns minimum data clock time t dclk 100 ns minimum data clock pulse width high t dclkpwh 30 ns minimum data clock pulse width low t dclkpwl 30 ns minimum load line t ld 30 ns minimum load line high to mixer clock on t mixclk 30 ns minimum data clock to load line high t clh 30 ns note 2: specifications at t a = +25 c and t a = +70 c are guaranteed by production test. specifications at t a = 0 c are guaran- teed by design and characterization. note 3: noise performance of the device is dependent on the noise contribution from the supply to v ref . use a low-noise supply for v ref . v cc and v ref can be connected together to share the same supply voltage if the supply for v cc exhibits low noise. note 4: total on-chip power dissipation is calculated as p diss = v cc x i cc + v ref x i ref + [11v - (i mix /4) x 115] x i mix . note 5: note that the lvds cwd lo clocks are dc-coupled. this is to ensure immediate synchronization when the clock is first turned on. an ac-coupled lo is problematic in that the rc time constant associated with the coupling capacitors and the input impedance of the pin causes there to be a period of time (related to the rc time constant) when the dc level on the chip side of the capacitor is outside the acceptable common-mode range and the lo swing does not exceed both the logic thresholds required for proper operation. this problem associated with ac-coupling would cause an inability to ensure synchronization among beam-forming channels. the lvds signal is terminated differentially with an external 100 resistor on the board. note 6: external 100 resistor terminates the lvds differential signal path. note 7: the mixer common-mode current (3.25ma/channel) is specified as the common-mode current in each of the differential mixer outputs (cw_qout+, cw_qout-, cw_iout+, cw_iout-). note 8: specification guaranteed only for dout driving din of the next device in a daisy-chain fashion. note 9: this response time does not include the cw output highpass filter. when switching to vga mode, the cw outputs stop drawing current and the output voltage goes to the rail. if a highpass filter is used, the recovery time can be excessive and a switching network is recommended as shown in the applications information section. note 10: see the ultrasound-specific imd3 specification in the applications information section. note 11: mixer output-voltage compliance is the range of acceptable voltages allowed on the cw mixer outputs. note 12: channel-to-channel gain-and-phase matching measured on 30 pieces during engineering characterization at room tem- perature. each mixer is used as a phase detector and produces a dc voltage in the iq plane. the phase is given by the angle of the vector drawn on that plane. multiple channels from multiple parts are compared to each other to produce the phase variation. note 13: transconductance is defined as the quadrature summing of the cw differential output current at baseband divided by the mixer? input voltage.
MAX2038 ultrasound vga integrated with cw octal mixer _______________________________________________________________________________________ 7 typical operating characteristics (figure 7, v cc = v ref = 4.75v to 5.25v, v gnd = 0, pd = 0, vg_clamp_mode = 1, f rf = 5mhz, capacitance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , t a = 0 c to +70 c. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) 0 1.0 0.5 2.0 1.5 3.0 2.5 3.5 4.5 4.0 5.0 0 5.0 7.5 2.5 10.0 12.5 15.0 17.5 20.0 overdrive phase delay vs. frequency MAX2038 toc01 frequency (mhz) overdrive phase delay (ns) v in1 = 35mv p-p differential v in2 = 87.5mv p-p differential gain = 20db -100 -90 -80 -70 -60 -50 -40 075 50 25 100 125 150 175 200 power-supply modulation ratio MAX2038 toc02 frequency (khz) psmr (dbc) v out = 1.5v p-p differential v mod = 50mv p-p , f carrier = 5mhz, gain = 10db -80 -70 -60 -50 -40 -30 -20 -10 0 -15 -5 5 15 25 35 two-tone ultrasound-specific imd3 vs. gain MAX2038 toc03 gain (db) imd3 (dbc) v out = 1v p-p differential f = 10mhz f = 2mhz f = 5mhz overload recovery time MAX2038 toc07 differential output 2.0v/div differential input 2.0v/div 400ns/div f = 5mhz output 100mv p-p to overload and back to 100mv p-p -100 -80 -90 -60 -70 -40 -50 -30 -10 -20 0 -15 5 -5 15 25 35 second harmonic distortion vs. gain MAX2038 toc04 gain (db) hd2 (dbc) v out = 1v p-p differential f = 12mhz f = 2mhz f = 5mhz -100 -80 -90 -60 -70 -40 -50 -30 -10 -20 0 -15 5 -5 15 25 35 third harmonic distortion vs. gain MAX2038 toc05 gain (db) hd3 (dbc) v out = 1v p-p differential f = 12mhz f = 2mhz f = 5mhz overload recovery time MAX2038 toc06 differential output 1.0v/div differential input 1.0v/div 400ns/div f = 5mhz output 1v p-p to overload and back to 1v p-p
MAX2038 ultrasound vga integrated with cw octal mixer 8 _______________________________________________________________________________________ 20 15 10 5 0 -5 -10 -15 -20 0.1 10 100 1 1000 large-signal bandwidth vs. frequency MAX2038 toc14 frequency (mhz) gain (db) v out = 1.5v p-p differential vg_ctl = +0.6v p-p differential 10 5 0 -5 -10 -15 -20 -25 -30 0.1 10 100 1 1000 large-signal bandwidth vs. frequency MAX2038 toc15 frequency (mhz) gain (db) v out = 1.5v p-p differential vg_ctl = +1.5v p-p 5 0 -5 -10 -15 -20 -25 -30 -35 0.1 10 100 1 1000 large-signal bandwidth vs. frequency MAX2038 toc16 frequency (mhz) gain (db) v out = 1v p-p differential vg_ctl = +1.7v p-p differential -25 -5 -15 15 5 25 35 -2.5 -0.5 -1.5 0.5 1.5 2.5 gain vs. differential analog control voltage (vg_ctl) MAX2038 toc11 vg_ctl (v p-p differential) f = 5mhz gain (db) 40 35 30 25 20 15 10 5 0 0.1 10 100 1 1000 large-signal bandwidth vs. frequency MAX2038 toc12 frequency (mhz) gain (db) v out = 1.5v p-p differential vg_ctl = -2v p-p differential 30 25 20 15 10 5 0 -5 -10 0.1 10 100 1 1000 large-signal bandwidth vs. frequency MAX2038 toc13 frequency (mhz) gain (db) v out = 1.5v p-p differential vg_ctl = -1v p-p differential -100 -90 -95 -80 -85 -75 -65 -70 -60 -15 5 -5 15 25 35 channel-to-channel crosstalk vs. gain MAX2038 toc08 gain (db) crosstalk (db) v out = 1.5v p-p differential f = 10mhz, adjacent channels -30 -110 1 10 100 channel-to-channel crosstalk vs. frequency -90 -100 MAX2038 toc09 frequency (mhz) crosstalk (db) -70 -80 -60 -50 -40 v out = 1v p-p differential gain = 10db, adjacent channels 0 10 20 30 40 50 -15 5 -5 15 25 35 output-referred noise voltage vs. gain MAX2038 toc10 gain (db) f = 5mhz output-referred noise voltage (nv/ hz) typical operating characteristics (continued) (figure 7, v cc = v ref = 4.75v to 5.25v, v gnd = 0, pd = 0, vg_clamp_mode = 1, f rf = 5mhz, capacitance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , t a = 0 c to +70 c. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.)
MAX2038 ultrasound vga integrated with cw octal mixer _______________________________________________________________________________________ 9 0 -5 -10 -15 -20 -25 -30 -35 -40 0.1 10 100 1 1000 large-signal bandwidth vs. frequency MAX2038 toc17 frequency (mhz) gain (db) v out = 0.5v p-p differential vg_ctl = +2v p-p differential -100 -80 -90 -60 -70 -40 -50 -30 -10 -20 0 01.5 0.5 1.0 2.0 2.5 3.0 harmonic distortion vs. differential output voltage MAX2038 toc18 differential output voltage (v p-p ) harmonic distortion (dbc) third harmonic second harmonic v out = 1v p-p differential f = 5mhz, gain = 10db -100 -90 -95 -80 -85 -70 -75 -65 -50 -60 -45 -55 -40 200 1100 500 800 1400 1700 2000 harmonic distortion vs. differential output load resistance MAX2038 toc19 differential output load ( ) harmonic distortion (dbc) third harmonic second harmonic v out = 1v p-p differential f = 5mhz, gain = 10db typical operating characteristics (continued) (figure 7, v cc = v ref = 4.75v to 5.25v, v gnd = 0, pd = 0, vg_clamp_mode = 1, f rf = 5mhz, capacitance to gnd at each of the vga differential outputs is 60pf, differential capacitance across the vga outputs is 10pf, r l = 1k , t a = 0 c to +70 c. typical values are at v cc = v ref = 5v, t a = +25 c, unless otherwise noted.) -100 -90 -95 -80 -85 -70 -75 -65 -45 -50 -55 -60 -40 565 25 45 85 105 harmonic distortion vs. differential output load capacitance MAX2038 toc20 differential output load (pf) harmonic distortion (dbc) third harmonic second harmonic v out = 1v p-p differential f = 5mhz, gain = 10db -100 -80 -90 -60 -70 -40 -50 -30 -10 -20 0 020 10 30 40 50 harmonic distortion vs. frequency MAX2038 toc21 frequency (mhz) harmonic distortion (dbc) v out = 1v p-p differential gain = 10db third harmonic second harmonic -70 -60 -50 -40 -10 -20 -30 0 015 510 2025 two-tone ultrasound-specific imd3 vs. frequency MAX2038 toc22 frequency (mhz) imd3 (dbc) v out = 1v p-p differential gain = 10db 0 20 15 50 10 5 25 30 35 40 45 0.40 -0.40 -0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.05 0.10 0.15 0.20 0.25 0.30 0.35 gain error histogram MAX2038 toc23 gain error (db) % of units sample size = 202 units, f in_ = 5mhz, gain = 10db -20 -10 -15 0 -5 10 5 15 20 -15 5 -5 15 25 35 output common-mode offset voltage vs. gain MAX2038 toc24 gain (db) offset voltage (mv) 0.1 10 100 differential output impedance magnitude vs. frequency MAX2038 toc25 frequency (mhz) | z out | 1 200 60 80 100 120 140 180 160
MAX2038 ultrasound vga integrated with cw octal mixer typical operating characteristics (continued) (figure 7, v cc = v ref = 4.75v to 5.25v, v gnd = 0, low_pwr = 0, m4_en = 0, cw_filter = 1, tmode = 0, pd = 0, cw_vg = 0, cw_m1 = 0, cw_m2 = 0, cw mixer outputs pulled up to 11v through four separate ?.1% 115 resistors, differential mixer inputs are driven from a low-impedance source. cw filter response (cw_filter = 1) MAX2038 toc26 frequency (mhz) loss (db) 14 12 8 10 4 6 2 -12 -10 -8 -6 -4 -2 0 2 4 -14 016 cw filter response (cw_filter = 0) MAX2038 toc27 frequency (mhz) loss (db) 14 12 8 10 4 6 2 -25 -20 -15 -10 -5 0 5 -30 016 cw imd3 vs. frequency (mode 1, v rf = 900mv p-p diff , v cc = v ref ) MAX2038 toc28 frequency (mhz) cw imd3 (dbc) 6 4 2 -53 -52 -51 -50 -49 -48 -47 -46 -54 0 8 4.75 5.00 5.25 input-referred noise vs. clutter voltage (mode 4, f_clutter = 1.25mhz at 1khz offset) MAX2038 toc29 clutter voltage (v p-p diff ) input-referred noise (nv/ hz) 1.5 1.0 0.5 2 4 6 8 10 12 14 0 0 2.0 10 ______________________________________________________________________________________
MAX2038 pin description pin name function 1 cwin2- cw mixer channel 2 inverting differential input 2 cwin2+ cw mixer channel 2 noninverting differential input 3 vgin3- vga channel 3 inverting differential input 4 vgin3+ vga channel 3 noninverting differential input 5, 10, 19, 24, 29, 34, 58, 79, 81, 96 gnd ground 6 cwin3- cw mixer channel 3 inverting differential input 7 cwin3+ cw mixer channel 3 noninverting differential input 8 vgin4- vga channel 4 inverting differential input 9 vgin4+ vga channel 4 noninverting differential input 11 cwin4- cw mixer channel 4 inverting differential input 12 cwin4+ cw mixer channel 4 noninverting differential input 13 ext_c1 external compensation. connect a 4.7f capacitor to ground as close as possible to the pin to bypass the internal biasing circuitry. 14 ext_c2 external compensation. connect a 4.7f capacitor to ground as close as possible to the pin to bypass the internal biasing circuitry. 15 ext_c3 external compensation. connect a 4.7f capacitor to ground as close as possible to the pin to bypass the internal biasing circuitry. 16, 42, 46, 54, 72, 82, 87 v cc 5v power supply. connect to an external +5v power supply. bypass each v cc supply to ground with 0.1f capacitors as close as possible to the pins. 17 vgin5- vga channel 5 inverting differential input 18 vgin5+ vga channel 5 noninverting differential input 20 cwin5- cw mixer channel 5 inverting differential input 21 cwin5+ cw mixer channel 5 noninverting differential input 22 vgin6- vga channel 6 inverting differential input 23 vgin6+ vga channel 6 noninverting differential input 25 cwin6- cw mixer channel 6 inverting differential input 26 cwin6+ cw mixer channel 6 noninverting differential input 27 vgin7- vga channel 7 inverting differential input 28 vgin7+ vga channel 7 noninverting differential input 30 cwin7- cw mixer channel 7 inverting differential input 31 cwin7+ cw mixer channel 7 noninverting differential input 32 vgin8- vga channel 8 inverting differential input 33 vgin8+ vga channel 8 noninverting differential input 35 cwin8- cw mixer channel 8 inverting differential input 36 cwin8+ cw mixer channel 8 noninverting differential input ultrasound vga integrated with cw octal mixer ______________________________________________________________________________________ 11
MAX2038 ultrasound vga integrated with cw octal mixer 12 ______________________________________________________________________________________ pin description (continued) pin name function 37, 93 v ref +5v reference supply. connect to a low-noise power supply. bypass to gnd with a 0.1? capacitor as close as possible to the pins. note that noise performance of the device is dependent on the noise contribution from the supply to v ref . use a low-noise supply for v ref . v cc and v ref can be connected together to share the same supply voltage if the supply for v cc exhibits low noise. 38 ext_res external resistor. connect a 0.1% 7.5k resistor to ground as close as possible to the pin to set the bias for the internal biasing circuitry. 39 cw_vg cw mixer vga enable. selects for vga or cw mixer operation. set cw_vg to a logic-high to enable the vgas while the cw mixers are powered down. set cw_vg to a logic-low to enable the cw mixers while the vgas are powered down. 40 pd power-down switch. drive pd high to set the device in power-down mode. drive pd low for normal operation. 41 cw_filter cw filter mode corner frequency select. selects in corner frequency of the internal lowpass filter for the cw path. set cw_filter to a logic-high for a corner frequency of 9.5mhz. set cw_filter to a logic-low for a corner frequency of 4.5mhz. 43 m4_en mode 4 enable. set m4_en to a logic-high to override the serial port and activate all 8 channels of the cw path. 44 low_pwr low-power enable. set high to enable low-power cw mixer mode for the device. 45 dout serial port data output. data output for ease of daisy-chaining cw channels for analog beamforming programming. 47 n.c. no connect. leave this pin unconnected. 48 lo8 cw lo input for channel 8. lo clock input for modes 3 and 4. 49 vgout8+ vga channel 8 noninverting differential output 50 vgout8- vga channel 8 inverting differential output 51 lo7 cw lo input for channel 7. lo clock input for modes 3 and 4. 52 vgout7+ vga channel 7 noninverting differential output 53 vgout7- vga channel 7 inverting differential output 55 lo6 cw lo input for channel 6. lo clock input for modes 3 and 4. 56 vgout6+ vga channel 6 noninverting differential output 57 vgout6- vga channel 6 inverting differential output 59 lo5 cw lo input for channel 5. lo clock input for modes 3 and 4. 60 vgout5+ vga channel 5 noninverting differential output 61 vgout5- vga channel 5 inverting differential output 62 vg_ctl- 63 vg_ctl+ vga analog gain control differential input. set the differential voltage to -2v for maximum gain (+29.5db), and to +2v for minimum gain (-12.5db). 64 lo_lvds- cw lvds lo inverting differential input. lo clock inverting input for modes 1 and 2. 65 lo_lvds+ cw lvds lo noninverting differential input. lo clock noninverting input for modes 1 and 2. 66 lo4 cw lo input for channel 4. lo clock input for modes 3 and 4. 67 vgout4+ vga channel 4 noninverting differential output 68 vgout4- vga channel 4 inverting differential output 69 lo3 cw lo input for channel 3. lo clock input for modes 3 and 4. 70 vgout3+ vga channel 3 noninverting differential output
MAX2038 ultrasound vga integrated with cw octal mixer ______________________________________________________________________________________ 13 pin name function 71 vgout3- vga channel 3 inverting differential output 73 lo2 cw lo input for channel 2. lo clock input for modes 3 and 4. 74 vgout2+ vga channel 2 noninverting differential output 75 vgout2- vga channel 2 inverting differential output 76 lo1 cw lo input for channel 1. lo clock input for modes 3 and 4. 77 vgout1+ vga channel 1 noninverting differential output 78 vgout1- vga channel 1 inverting differential output 80 din serial port data input. data input to program the serial shift registers. 83 clk serial port data clock. clock input for programming the serial shift registers. 84 cw_m1 cw mode select input 1. input for programming beamforming mode 1, 2, 3, or 4. see table 1 for mode programming details. 85 cw_m2 cw mode select input 2. input for programming beamforming mode 1, 2, 3, or 4. see table 1 for mode programming details. 86 vg_clamp_ mode vga clamp mode enable. drive vg_clamp_mode high to enable high vga clamp mode. vga output is clamped at typically 2.4v p-p differential. drive vg_clamp_mode low to enable low vga clamp mode. vga output is clamped at typically 2.8v p-p differential. 88 load serial port load. loads the data from the serial shift registers into the i/q phase dividers. pull load bus from high to low and from low to high for programming the i/q phase dividers. 89 cw_qout+ cw mixer noninverting differential quadrature output. cw mixer output for eight quadrature mixers combined. 90 cw_qout- cw mixer inverting differential quadrature output. cw mixer output for eight quadrature mixers combined. 91 cw_iout- c w m i xer inver ti ng d i ffer enti al in- p hase outp ut. c w m i xer outp ut for ei g ht i n- p hase m i xer s com b i ned . 92 cw_iout+ cw mixer noninverting differential in-phase output. cw mixer output for eight in-phase mixers combined. 94 vgin1- vga channel 1 inverting differential input 95 vgin1+ vga channel 1 noninverting differential input 97 cwin1- cw mixer channel 1 inverting differential input 98 cwin1+ cw mixer channel 1 noninverting differential input 99 vgin2- vga channel 2 inverting differential input 100 vgin2+ vga channel 2 noninverting differential input ?p exposed pad. internally connected to gnd. connect ep to a large pcb ground plane to maximize thermal performance. pin description (continued)
MAX2038 ultrasound vga integrated with cw octal mixer 14 ______________________________________________________________________________________ detailed description the MAX2038 is an 8-channel vga integrated with a programmable octal quadrature mixer array designed for ultrasound imaging and doppler applications. the device is optimized for efficient power consumption, high dynamic range, and for exceptionally low noise performance. the vga path features differential inputs, analog variable gain control, differential outputs for direct adc drive, and a selectable output voltage clamp to avoid adc overdrive. the integrated octal quadrature mixer array includes serial programmable lo phase generators for cwd beamforming applica- tions. the lo phase dividers can be programmed for 4, 8, or 16 quadrature phases. lowpass filters are inte- grated at the input paths of each cw mixer. the out- puts for the mixers are summed into single i/q differential current outputs. the MAX2038 also integrates an octal quadrature mixer array and programmable lo phase generators for a complete continuous wave (cw) doppler beamforming solution. the lo phase selection for each channel is programmed using a digital serial interface and a sin- gle high-frequency clock, or the los for each complex mixer pair can be directly driven using separate 4 x lo clocks. the serial interface is designed to allow multiple devices to be easily daisy chained in order to minimize program interface wiring. the lo phase dividers can be programmed to allow 4, 8, or 16 quadrature phases. the input path of each cw mixer consists of a selec- table lowpass filter for optimal cwd noise performance. the outputs of the mixers are summed into single i and q differential current outputs. the mixers and lo gen- erators are designed to have exceptionally low noise performance of -155dbc/hz at 1khz offset from a 1.25mhz carrier, measured with 900mv p-p differential clutter signal. variable gain amplifier (vga) the MAX2038? vgas are optimized for high linearity, high dynamic range, and low output-noise performance, making this component ideal for ultrasound imaging applications. the vga paths also exhibit a channel-to- channel crosstalk of -80db at 10mhz and an absolute gain error of less than ?.25db for minimal channel-to- channel focusing error in an ultrasound system. each vga path includes circuitry for adjusting analog gain, an output buffer with differential output ports (vgout_+, vgout_-) for driving adcs, and differential input ports (vgin_+, vgin_-), which are ideal for directly interfac- ing to the max2034 quad lna. see the high-level wave mixer and programmable beamformer functional diagram for details. the vga has an adjustable gain range from -12.5db to +29.5db, achieving a total dynamic range of 42db (typ). the vga gain can be adjusted through the differ- ential gain control inputs vg_ctl+ and vg_ctl-. set the differential gain-control input voltage at +2v for min- imum gain and -2v for maximum gain. the differential analog control common-mode voltage is 3v (typ). gnd v cc +5v v ref vg_ctl+ vg_ctl- vg_clamp_mode vgout1+ vgout1- vgout8+ vgout8- cw_iout+ cw_iout- vgin1+ vgin1- vgin8+ vgin8- low_pwr pd cw_vg cw_filter vga 50 50 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +5v (low noise) ? ? ? ? ? ? ? ? ? vga i&q 50 50 cwin1+ cwin1- ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? cw_qout+ cw_qout- i&q cwin8+ cwin8- MAX2038 high-level wave mixer and programmable beamformer _ functional diagram
MAX2038 ultrasound vga integrated with cw octal mixer ______________________________________________________________________________________ 15 vga clamp a clamp is provided to limit the vga output signals to avoid overdriving the adc or to prevent adc satura- tion. set vg_clamp_mode low to clamp the vga dif- ferential outputs at 2.4v p-p . set the vg_clamp_mode high to disable the clamp. power-down the device can also be powered down with pd. set pd to logic-high for power-down mode. in power-down mode, the device draws a total supply current of 27ma. set pd to a logic-low for normal operation. overload recovery the device is also optimized for quick overload recovery for operation under the large input-signal conditions that are typically found in ultrasound input buffer imaging applications. see the typical operating characteristics for an illustration of the rapid recovery time from a trans- mit-related overload. octal continuous wave (cw) mixer the MAX2038 cw mixers are designed using an active double-balanced topology. the mixers achieve high dynamic range and high linearity performance, with exceptionally low noise, which is ideal for ultrasound cwd signal reception. the octal quadrature mixer array provides noise performance of -155dbc/hz at 1khz from a 1.25mhz carrier, and a two-tone third- order ultrasound specific intermodulation product of typically -50dbc. see the ultrasound-specific imd3 specification in the applications information section . the octal array exhibits quadrature and in-phase differ- ential current outputs (cw_qout+, cw_qout-, cw_iout+, cw_iout-) to produce the total cwd beamformed signal. the maximum differential current output is typically 3ma p-p and the mixer output-compli- ance voltage ranges from 4.75v to 12v. channel 1 i/q divider phase selector 5 5-bit sr 5-bit sr 5-bit sr iq i q din clk lo_lvds+ lo_lvds- cwin1 cwin2 cwin8 gnd cw_m2 cw_m1 cw_iout+ dout low_pwr pd cw_iout- cw_qout- cw_qout+ cw_iout2+ cw_qout2- load lo1 lo2 lo8 v cc v ref cw_filter m4_en ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? MAX2038 i q channel 2 i/q divider phase selector 5 channel 8 i/q divider phase selector 5 high-level cw mixer and programmable beamformer functional diagram
MAX2038 ultrasound vga integrated with cw octal mixer 16 ______________________________________________________________________________________ cw mixer output summation the outputs from the octal mixer array are summed internally to produce the total cwd summed beam- formed signal. the octal array produces eight differen- tial quadrature (q) outputs and eight differential in-phase (i) outputs. all quadrature and in-phase out- puts are summed into single i and q differential current outputs (cw_qout+, cw_qout-, cw_iout+, cw_iout-). lo phase select the lo phase dividers can be programmed through the shift registers to allow for 4, 8, or 16 quadrature phases for a complete cw beamforming solution. cwd beamforming modes there are four separate modes of operating the cwd beamformer. see table 1 for a summary of the different modes of operation. the mode of operation can be selected by the cw_m1 and cw_m2 logic inputs. phase generation is controlled through the serial inter- face. see the serial interface section in the applications information section for details on how to program for dif- ferent quadrature phases. mode 1 for mode 1 operation, the lo_lvds input frequency is typically 16 x f lo . as the cwd lo frequency range is 1mhz to 7.5mhz, the input frequency ranges from 16mhz to 120mhz. this high lo clock frequency requires a differential lvds input. the 16 x f lo input is then divided by 16 to produce 16 phases. these 16 phases are generated for each of the 8 channels and programmed for the selected phase by a serial shift register. each channel has a corresponding 5-bit shift register, which is used to program the output phase of the divide-by-16 circuit. the first 4 bits of the shift regis- ter are for programming the 16 phases, the fifth bit turns each channel on/off individually. for mode 1, set both cw_m1 and cw_m2 to a logic-low. cw_m1 cw_m2 mode lo input frequency clock interface phase resolution no. of clock inputs per chip program by serial shift register (ssr) no. of useful bits in ssr no. of don?- care bits in ssr 0 0 1 16 x lvds 16 phases 1 yes 4 0 0 1 2 8 x lvds 8 phases 1 yes 3 1 msb 1 0 3 4 x 3v cmos 4 phases 8 yes 2 2 msbs 1 1 4 4 x 3v cmos quadrature provided 8 no n/a n/a table 1. summary of cwd beamforming methods mode 1 cw_m1 = 0 cw_m2 = 0 msb lsb shutdown dcba sd phase (deg) (b0) (b1) (b2) (b3) (b4) 0 0 0 0 0 0/1 22.5 0 0 0 1 0/1 45 0 0 1 0 0/1 67.5 0 0 1 1 0/1 90 0 1 0 0 0/1 112.5 0 1 0 1 0/1 135 0 1 1 0 0/1 157.5 0 1 1 1 0/1 180 1 0 0 0 0/1 202.5 1 0 0 1 0/1 225 1 0 1 0 0/1 247.5 1 0 1 1 0/1 270 1 1 0 0 0/1 292.5 1 1 0 1 0/1 315 1 1 1 0 0/1 337.5 1 1 1 1 0/1 table 2. mode 1 logic table (b4 = 0: channel on/b4 = 1: channel off) n/a = not applicable.
MAX2038 ultrasound vga integrated with cw octal mixer ______________________________________________________________________________________ 17 mode 2 the lo_lvds input frequency is 8 x f lo (typ) for mode 2 operation. the cwd lo frequency range is 1mhz to 7.5mhz, and the input frequency ranges from 8mhz to 60mhz. this high lo clock frequency requires a differ- ential lvds input. the 8 x f lo input is then divided by 8 to produce 8 phases. these 8 phases are generated for each of the 8 channels and programmed for the selected phase by the serial shift register. note that the serial shift register is common to modes 1, 2, 3, and where each channel has a corresponding 5-bit shift register, which is used to program the output phase. however, since mode 2 generates 8 phases only, 3 of the 4 phase-programming bits are used; 5 bits are still loaded per channel using the serial shift register, but the phase-programming msb is a don?-care bit. the fifth bit in the shift register always turns each channel on/off individually. for mode 2, set cw_m1 to a logic- low and set cw_m2 to a logic-high. see table 3. mode 3 the lo_lvds input is not used in this mode. separate 4 x f lo clock inputs are provided using lo1?o8 for each channel. the cwd lo frequency range is 1mhz to 7.5mhz, and the input frequency provides ranges from 4mhz to 30mhz. note that the lo clock frequency can utilize 3v cmos inputs. the 4 x f lo lo1?o8 inputs are divided by 4 to produce 4 phases. these 4 phases are generated for each of the 8 channels and programmed for the selected phase by the serial shift register. for mode 3, 4 phases are generated, and only 2 of the 4 phase-programming bits are required where the 2-phase programming msbs are ?on?-care?bits. for mode 3, set cw_m1 to a logic-high and set cw_m2 to a logic-low. see table 4. mode 4 the lo_lvds input is not used in this mode. the appropriate phases are externally provided using sepa- rate 4 x f lo lo1?o8 inputs for each channel. a 4 x f lo input is required so the device can internally generate accurate duty-cycle independent quadrature lo drives. note that the serial shift register is not used in this mode. the cwd lo frequency range is 1mhz to 7.5mhz and the input frequency ranges from 4mhz to 30mhz. the appropriate inputs are provided at lo1 to lo8. a reset line is provided to the customer so that they can synchronize all the cwd channels. the reset line is implemented through the reset. for mode 4, set both cw_m1 and cw_m2 to logic-high. see table 5. shutdown mode 2 cw_m1 = 0 cw_m2 = 1 dcba sd phase (deg) (b0) (b1) (b2) (b3) (b4) 0 dc000 0/1 45 dc 0 0 1 0/1 90 dc 0 1 0 0/1 135 dc 0 1 1 0/1 180 dc 1 0 0 0/1 225 dc 1 0 1 0/1 270 dc 1 1 0 0/1 315 dc 1 1 1 0/1 table 3. mode 2 logic table (dc = dont care, b4 = 0: channel on/b4 = 1: channel off) mode 3 cw_m1 = 1 cw_m2 = 0 shutdown dcba sd phase (deg) (b0) (b1) (b2) (b3) (b4) 0 dc dc 0 0 0/1 90 dc dc 0 1 0/1 180 dc dc 1 0 0/1 270 dc dc 1 1 0/1 table 4. mode 3 logic table (dc = dont care, b4 = 0: channel on/b4 = 1: channel off) mode 4 cw_m1 = 1 cw_m2 = 1 shutdown dcba sd phase (deg) (b0) (b1) (b2) (b3) (b4) serial bus not used in mode 4 n/a n/a n/a n/a n/a table 5. mode 4 logic table n/a = not applicable.
MAX2038 ultrasound vga integrated with cw octal mixer 18 ______________________________________________________________________________________ synchronization figure 1 illustrates the serial programming of the 8 indi- vidual channels through the serial data port. note that the serial data can be daisy chained from one part to another, allowing a single data line to be used to pro- gram multiple chips in the system. cw lowpass filter the MAX2038 also includes selectable lowpass filters between each cw differential input pair and corre- sponding mixer input. shunt capacitors and resistors are integrated on chip for high band and low band. the parallel capacitor/resistor networks, which appear differ- entially across each of the cw differential inputs, are selectable through the cw_filter. drive cw_filter high to set the corner frequency of the filter to be f c = 9.5mhz. drive cw_filter low to set the corner fre- quency equal to f c = 4.5mhz. the cw_vg allows the fil- ter inputs to be disconnected from input nodes (internal to chip) to prevent overloading the lna output and to not change the pw input common-mode voltage. vga and cw mixer operation during normal operation, the MAX2038 is configured such that either the vga path is enabled while the mixer array is powered down (vga mode), or the quadrature mixer array is enabled while the vga path is powered down (cw mode). during vga mode, besides powering down the cw mixer array, the differential inputs to the lowpass filters and cw mixers also are internally discon- nected from the input nodes, making the cw differential inputs (cwin_+, cwin_-) high impedance. the cw mode disconnects the vga inputs internally from the input ports of the device. for vga mode, set cw_vg to a logic-high, while for cw mode, set cw_vg to a logic-low. power-down and low-power modes during device power-down, both the vga and cw mixer are disabled regardless of the logic set at cw_vg. both the vga and cw mixer inputs are high impedance since the internal switches to the inputs are all disconnected. the total supply current of the device reduces to 27ma. set pd to a logic-high for device power-down. a low-power mode is available to lower the required power for cwd operation. when selected, the complex mixers operate at lower quiescent currents and the total per-channel current is lowered to 53ma. note that operation in this mode slightly reduces the dynamic performance of the device. table 6 shows the logic function of standard operating modes. channel 1 data_in data_out clock ab c dsd b3 b2 b1 b0 b4 channel 2 ab c dsd b3 b2 b1 b0 b4 channel 3 ab c dsd b3 b2 b1 b0 b4 channel 4 ab c dsd b3 b2 b1 b0 b4 channel 5 ab c dsd b3 b2 b1 b0 b4 channel 6 ab c dsd b3 b2 b1 b0 b4 channel 7 ab c dsd b3 b2 b1 b0 b4 channel 8 ab c dsd b3 b2 b1 b0 b4 figure 1. data flow of serial shift register pd input cw_vg input low_pwr vga cw mixer internal switch to vga internal switch to lpf and cw mixer 5v v cc current consumption (ma) 11v v mix current consumption (ma) 1 1 n/a off off off off 27 0 1 0 n/a off off off off 27 0 0 0 0 off on off on 245 106 0 0 1 off on off on 245 53 0 1 n/a on off on off 204 0 table 6. logic function of standard operating modes n/a = not applicable.
MAX2038 ultrasound vga integrated with cw octal mixer ______________________________________________________________________________________ 19 applications information mode select response time the mode select response time is the time that the device takes to switch between cw and vga modes. one possible approach to interfacing the cw outputs to an instrumentation amplifier used to drive an adc is shown in figure 2. in this implementation, there are four large-value (in the range of 470nf to 1f) capacitors between each of the cw_iout+, cw_iout-, cw_qout+, cw_qout- outputs and the circuitry they are driving. the output of the cw mixer usually drives the input of an instrumentation amplifier made up of op amps whose input impedance is set by common-mode setting resistors. there are clearly both a highpass corner and a lowpass corner present in this output network. the lowpass cor- ner is set primarily by the 115 mixer pullup resistors, the series 50 resistors, and the shunt 0.022? capaci- tor. this lowpass corner is used to filter a combination of lo leakage and upper sideband. the highpass cor- ner, however, is of a larger concern due to the fact that it is dominated by the combination of a 1? dc-block- ing capacitor and the pair of shunt 31.6k resistors. if drawn, the simplified dominant highpass network would look like figure 3. the highpass pole in this case is at f p = 1/(2 x pi x rc) ~ 5hz. note that this low highpass corner frequency is required in order to filter the downconverted clutter tone, which appears at dc, but not interfere with cwd imaging at frequencies as low as 400hz. for example, if one want- ed to use cwd down to 400hz, then a good choice for the highpass pole would be at least a decade below this (< 40hz) as not to incur rolloff due to pole. remember, if the highpass pole is put at 400hz, the response is 3db down at that corner frequency. the placement of the highpass pole at 5hz in the above example is between the dc and 40hz limitations just discussed. the bottom line is that any reasonably sized dc block between the output of the mixer and the instrumentation amplifier will pose a significant time constant that slows the mode select switching speed. an alternative solution to the approach in figure 2, which enables faster mode select response time, is shown in figure 4. in figure 4, the outputs of the cwd mixers are dc- coupled into the inputs of the instrumentation ampli- fiers. therefore, the op amps must be able to accom- modate the full compliance range of the mixer outputs, which is a maximum of 11v when the mixers are dis- abled, down to the 5v supply of the MAX2038 when the mixers are enabled. the op amps can be powered from 11v for the high rail and 5v for the low rail, requir- ing a 6v op amp. 115 115 1 f 1 f 0.022 f 31.6k 31.6k 50 cw_iout+ cw_iout- figure 2. typical example of a cw mixer? output circuit 1 f 31.6k figure 3. simplified circuit of highpass pole +11v +5v figure 4. improved mode select response time achieved with dc-coupled input to instrumentation amplifier
MAX2038 ultrasound vga integrated with cw octal mixer 20 ______________________________________________________________________________________ serial interface the serial interface of the MAX2038 programs the lo for 16, 8, or 4 quadrature phases using a serial shift regis- ter implementation. data is shifted into the device on din. the serial shift register clock is applied to the clk input. the serial shift register has 5 bits per channel. the first 4 bits are for phase programming, and the fifth bit enables or disables each channel of the mixer array. each mixer can be programmed to 1 of 16 phases; therefore, 4 bits are required for each channel for pro- gramming. the master high-frequency mixer clock is applied to differential inputs lo_lvds+ and lo_lvds- (for modes 1 and 2) and lo_ (for modes 3 and 4). the load input is provided to allow the user to load the phase counters with the programming values to gener- ate the correct lo phases. the input signals for mixing are applied to the eight differential inputs, cwin_+ and cwin_-. the summed i/q baseband differential outputs are provided on cw_iout+/- and cw_qout+/-. cw_m1 and cw_m2 are used to select one of the four possible modes of operation. see table 1. the serial interface is designed to allow multiple devices to be easily daisy chained in order to minimize program interface wiring. dout is available for this daisy-chain function. programming the beamformer during normal cwd operation, the mixer clock at lo_ or lo_lvds+/- is on and the programming signals on din, clk, and load are off. (load = high, clk = low, and din = don? care, but fixed to a high or low). to start the programming sequence, turn off the mixer clock. data is shifted into the shift register at a recommended 10mhz programming rate or 100ns minimum data clock period/time. see figure 5 for timing details. after the shift registers are programmed, pull the load bus to logic-low and then back to logic-high to load the internal counters into i/q phase divider/selectors with the proper values. load must remain low for a mini- mum time of t clh . the user turns on the mixer clock to start beamforming. the clock must turn on such that it starts at the beginning of a mixer clock cycle. din clk load t dclkpwh t dclkpwl t ld t clh t dclk t dsu t hld t ldmixclk mixer clock on mixer clock on mixer clock off mixer clock on mixer clock off mixer clock off mixer clock on figure 5. shift register timing diagram
MAX2038 ultrasound vga integrated with cw octal mixer ______________________________________________________________________________________ 21 cw mixer output summation the maximum differential current output is typically 3ma p-p and the mixer output compliance voltage ranges from 4.75v to 12v per mixer channel. the mixer common-mode current in each of the differential mixer outputs is typically 3.25ma. the total summed current would equal n x 3.25ma in each of the 115 load resistors (where n = number of channels). in this case, the quiescent output voltage at +v sum and -v sum out- puts would be 11v - (n x 3.25ma x 115) = 11v - (8 x 3.25ma x 115) = 8.05v. the voltage swing at each out- put, with one channel driven at max output current (dif- ferential 3ma p-p ) while the other channels are not driven, would be 1.5ma p-p x 115 or 174mv p-p and the differential voltage would be 348mv p-p . the voltage compliance range is defined as the valid range for +v sum and -v sum in this example. external compensation external compensation is required for bypassing inter- nal biasing circuitry. connect as close as possible a 4.7? capacitor from ext_c1, ext_c2, and ext_c3 (pins 13, 14, 15) to ground. external bias resistor an external resistor at ext_res is required to set the bias for the internal biasing circuitry. connect, as close as possible, a 7.5k (0.1%) resistor from ext_res (pin 38) to ground. analog input and output coupling in typical applications, the MAX2038 is being driven from a low-noise amplifier (such as the max2034) and the vga is typically driving a discrete differential anti-alias fil- ter into an adc (such as the max1436 octal adc). the differential input impedance of the MAX2038 is typically 240 . the differential outputs of the vga are capable of driving a differential load capacitance to gnd at each of the vga differential outputs of 60pf, and differential capacitance across the vga outputs is 10pf, r l = 1k . the differential outputs have a common-mode bias of approximately 3.75v. ac-couple these differen- tial outputs if the next stage has a different common- mode input range. ultrasound-specific imd3 specification unlike typical communications specifications, the two input tones are not equal in magnitude for the ultra- sound-specific imd3 two-tone specification. in this measurement, f 1 represents reflections from tissue and f 2 represents reflections from blood. the latter reflec- tions are typically 25db lower in magnitude, and hence the measurement is defined with one input tone 25db lower than the other. the imd3 product of interest (f 1 - (f 2 - f 1 )) presents itself as an undesired doppler error signal in ultrasound applications. see figure 6. board layout the pin configuration of the MAX2038 is optimized to facilitate a very compact physical layout of the device and its associated discrete components. a typical application for this device might incorporate several devices in close proximity to handle multiple channels of signal processing. the exposed pad (ep) of the MAX2038? tqfp-ep package provides a low thermal-resistance path to the die. it is important that the pcb on which the MAX2038 is mounted be designed to conduct heat from the ep. in addition, provide the ep with a low-inductance path to electrical ground. the ep must be soldered to a ground plane on the pcb, either directly or through an array of plated via holes. -25db ultrasound imd3 f 1 - (f 2 - f 1 )f 2 + (f 2 - f 1 ) f 1 f 2 figure 6. ultrasound imd3 measurement technique
MAX2038 ultrasound vga integrated with cw octal mixer 22 ______________________________________________________________________________________ 12 h 12 h one channel one channel to 12-bit imaging adc to q channel cwd adc to i channel cwd adc cwd i/q lo cwd q channels in 0.1 f 0.1 f lo divider +v mix +v mix 50 100nf 100nf 100nf +v -v +v in 100nf 100nf zin in control d2, d1, d0 vg_ctl+ vg_ctl- vgin_+ vgin_- cwin_+ cwin_- cw_vg cw_filter vgout_+ vgout_- cw_iout+ cw_iout- cw_qout- cw_qout+ third-order butterworth anti-alias filter v cc v ref gnd 115 115 115 115 MAX2038 50 cwd i channels in max2034 figure 7. typical per-channel ultrasound imaging application
MAX2038 ultrasound vga integrated with cw octal mixer maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 23 2009 maxim integrated products is a registered trademark of maxim integrated products, inc. cwin6- gnd vgin6- cwin5+ vgin5+ vgin5- cwin2- 1 2 3 4 5 6 7 8 9 10111213141516 171819202122232425 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51 cwin5- gnd vgin6+ v cc ext_c2 ext_c1 gnd vgin4+ cwin4+ cwin4- ext_c3 cwin3+ cwin3- vgin3- cwin2+ gnd vgin3+ vgin4- vgout7- v cc lo6 vgout6- gnd lo5 vgout2- vgout7+ lo7 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 din gnd v cc cw_m1 vgin2+ gnd vgout1- vgout1+ lo1 vgout8+ lo8 n.c. v cc dout low_pwr m4_en v cc cw_filter pd cw_vg ext_res v ref cwin8+ gnd vgin8+ vgin8- cwin7+ cwin7- gnd vgin7+ vgin7- cwin6+ *ep *ep = exposed pad vgout8- MAX2038 top view vgout6+ vgout5- vg_ctl- vg_ctl+ lo_lvds+ lo4 vgout4+ vgout5+ lo_lvds- vgout4- lo3 vgout3+ v cc lo2 vgout2+ vgout3- load cw_qout+ cw_qout- cw_iout+ v cc vg_clamp_mode cw_m2 cw_iout- vgin1+ gnd cwin1- vgin2- vgin1- v ref cwin1+ clk cwin8- tqfp pin configuration package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. 100 tqfp-ep c100e+3 21-0116 chip information process: silicon complementary bipolar

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