general description the MAX2235 low-voltage, silicon rf power amplifier (pa) is designed for use in the 900mhz frequency band. it operates directly from a single +2.7v to +5.5v supply, making it suitable for use with 3-cell nicd or 1-cell li-ion batteries. the device delivers +30dbm (1w) typical out- put power from a +3.6v supply or +28dbm from a +2.7v supply. the MAX2235? gain is adjustable over a 37db range. a power-control pin controls gain and bias to maintain optimum efficiency, even at lower output power levels, thus extending the operating life of the battery. at +30dbm output power, efficiency is typically 47%. an additional power-saving feature is a shutdown mode that typically reduces supply current below 1?. a key feature of this pa is its autoramping capability. during turn-on and turn-off periods, the rf envelope is controlled to approximate a raised cosine on the rising and falling edge, thereby minimizing transient noise and spectral splatter. the ramp time is set by selecting the value of an external capacitor. the MAX2235 is intended for use in constant envelope applications such as amps, two-way paging, or fsk- based communications in the 900mhz ism band. the device is available in a thermally enhanced 20-pin tssop package with a heat slug. applications 900mhz ism-band applications two-way pagers analog cellular phones microcellular gsm (power class 5) wireless data networks features 800mhz to 1000mhz operation high output power at 836mhz +32.5dbm at +5.0v +30dbm at +3.6v +29dbm at +3.0v +28dbm at +2.7v +2.7v to +5.5v single-supply operation automatic power-up/power-down ramp direct on/off keying (ook) without intersymbol interference or vco pulling 37db power-control range 47% efficiency <1a supply current in shutdown mode small 20-pin tssop package with heat slug MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications ________________________________________________________________ maxim integrated products 1 20 19 18 17 16 15 14 13 1 2 3 4 5 6 7 8 gc shdn gnd gnd v cc v cc gnd rfin top view rfout rfout gnd gnd v cc gnd gnd v cc 12 11 9 10 ref ramp gnd v cc MAX2235 tssop-ep note: the ground of the output stage is connected to the underside metal slug. MAX2235 shdn gc rfin ramp bias v cc v cc v cc v cc ref note: solder underside of metal slug to board gnd plane. rfout gnd gnd gnd 15, 16 6, 7, 10 2 1 11 4 3 5 8, 9 12 19 20 13, 14, 17, 18, slug vga functional diagram 19-1463; rev 2; 10/00 part MAX2235eup -40? to +85? temp. range pin-package 20 tssop-ep evaluation kit available pin configuration ordering information for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com.
MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications 2 _______________________________________________________________________________________ absolute maximum ratings dc electrical characteristics (v cc = +2.7v to +5.5v, gc = ramp = ref = unconnected, no input signal applied, t a = -40? to +85?, unless otherwise noted. typical values are at v cc = +3.6v and t a = +25?.) 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 to gnd ...........................................................-0.3v to +6.5v shdn to gnd.............................................-0.3v to (v cc + 0.3v) gc to gnd .................................................-0.3v to (v cc + 0.3v) rf input power .................................................+13dbm (20mw) maximum load mismatch without damage, v cc = +2.7v to +3.4v, any load phase angle, any duration.......................................................................20:1 maximum load mismatch without damage, v cc = +3.4v to +5.5v, any load phase angle, any duration.........................................................................8:1 continuous power dissipation (t a = +70?) tssop (derate 80mw/? above t a = +70?) ..................6.4w operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? shdn = gnd (note 1) (note 2) v shdn > 2.3v, v gc > 0.6v v shdn < 0.5v, v gc < 0.4v 2.7v < v cc < 3.4v, shdn = gnd, t a = +55? v shdn = 2.0v v shdn < 0.5v conditions 0.5 100 v 0.5 v il v 2.0 v ih shdn logic high shdn logic low v 2.0 2.2 2.4 v gcnom gc open-circuit voltage ? -10 1.0 i gc gc input current -0.5 0.5 i shdn shutdown supply current ? 2 0.5 ? -0.5 0.5 i inshdn shdn input current units min typ max symbol parameter v gc < 0.4 ma 20 i stby standby supply current
MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications _______________________________________________________________________________________ 3 note 1: +25? guaranteed by production test, <+25? guaranteed by design and characterization. note 2: max guaranteed by production test, min guaranteed by design and characterization. note 3: guaranteed by design and characterization. note 4: for optimum performance at a given frequency, design the output matching network for maximum output power. note 5: gain is monotonic with v gc . note 6: 0.068? capacitor from ramp to ref. time is measured from shdn low-to-high transition to +29dbm output power, or from shdn high-to-low transition to -25dbm output power. note 7: harmonics measured on the evaluation kit, which provides some harmonic attenuation in addition to the rejection provided by the ic. the combined suppression is specified. p rfin adjusted to give p rfout = +24dbm p rfout = +30dbm p rfin = 0dbm, v gc adjusted to give p rfout = 24dbm 315 610 average supply current % 47 pae power added efficiency 0.6v < v gc < 2.3v db 37 db 24 26 g p power gain gain-control range (note 5) mw/? 1.6 dp/dt auto-power ramping-up maximum slope (note 6) input vswr relative to input impedance in operating mode v cc = 2.7v to 5.5v, 6:1 vswr at any phase angle 1.5:1 ? vswr standby mode input vswr change 50 ? source impedance dbc -60 maximum nonharmonic spurious output due to load mismatch 1.5:1 vswr input vswr mw/? -1.3 dp/dt auto-power ramping-down minimum slope (note 6) 30khz bw at offset = 45mhz dbm -90 noise power 40 48 p rfin = +7dbm dbc 30 38 harmonic suppression (note 7) ma 305 i cc p rfin = 0dbm db 25 36 off-isolation v shdn = 0.5v gc = gnd ac electrical characteristics (MAX2235 evaluation kit, gc = unconnected, p rfin adjusted to give p rfout = +30dbm, f rfin = 836mhz, v cc = v shdn = +3.6v, t a = +25?, unless otherwise noted.) (note 3) conditions units min typ max symbol parameter v cc = 2.7v 28.0 v cc = 3.0v, t a = t min to t max 25.5 v cc = 3.0v (note 4) 27.0 28.7 v cc = 3.6v 30.3 v cc = 5.0v dbm 32.5 p rfout minimum output power mhz 800 1000 f rfin operational frequency range (note 4)
MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications 4 _______________________________________________________________________________________ typical operating characteristics (MAX2235 evaluation kit, gc = unconnected, f rfin = 836mhz, v cc = v shdn = +3.6v, t a = +25?, unless otherwise noted.) 0 200 100 400 300 600 500 700 01015 5 20253035 supply current vs. output power MAX2235 toc01 output power (dbm) i cc (ma) t a = -40? t a = +25? t a = +85? -20 0 -10 20 10 30 40 0 1.0 0.5 1.5 2.0 2.5 output power vs. voltage at gc pin MAX2235 toc02 v gc (v) output power (dbm) p rfin = 0dbm t a = -40 c t a = +25 c t a = +85 c 0 10 5 20 15 30 25 35 -25 -15 -10 -20 -5 0 5 10 output power vs. input power MAX2235 toc03 input power (dbm) output power (dbm) v cc = +5.0v v cc = +3.6v v cc = +3.0v v cc = +2.7v 0 10 5 20 15 30 25 35 -25 -15 -10 -20 -5 0 5 10 output power vs. input power and temperature MAX2235 toc04 input power (dbm) output power (dbm) t a = -40 c t a = +25 c t a = +85 c 0 20 10 40 30 50 60 01520 5 10 253035 efficiency vs. output power MAX2235 toc07 output power (dbm) efficiency (%) v cc = +5.0v v cc = +3.6v v cc = +3.0v v cc = +2.7v -60 -40 -50 -20 -30 -10 0 -25 -10 -5 -20 -15 0 5 10 second and third harmonics vs. input power MAX2235 toc05 input power (dbm) harmonic power (dbm) 2nd 3rd 0 10 5 20 15 30 25 35 820 830 835 825 840 845 850 855 output power vs. frequency MAX2235 toc06 input frequency (mhz) output power (dbm) p rfin = +3dbm p rfin = -5dbm p rfin = -13dbm p rfin = -21dbm matched at 836mhz 0 10 5 20 15 30 25 35 01015 5 20253035 power gain vs. output power MAX2235 toc08 output power (dbm) power gain (db) v cc = +5.0v v cc = +3.6v v cc = +3.0v 40 v cc = +2.7v 0 10 5 20 15 35 30 25 40 010 5 1520253035 power gain vs. output power and temperature MAX2235 toc09 output power (dbm) power gain (db) t a = -40 c t a = +25 c t a = +85 c
MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications _______________________________________________________________________________________ 5 0 400 200 800 600 1200 1000 1400 04060 20 80 100 120 rise time vs. ramping capacitance MAX2235 toc10 capacitance (nf) rise time ( s) full power = +20dbm full power = +10dbm full power = +30dbm typical operating characteristics (continued) (MAX2235 evaluation kit, gc = unconnected, f rfin = 836mhz, v cc = v shdn = +3.6v, t a = +25?, unless otherwise noted.) 0 400 200 800 600 1000 1200 04060 20 80 100 120 fall time vs. ramping capacitance MAX2235 toc11 capacitance (nf) fall time ( s) full power = +20dbm full power = +10dbm full power = +30dbm name function 1 rfin rf input. a dc blocking capacitor in series with rfin is required. the value of the capacitor depends on the operating frequency. pin pin description 2 gnd gnd connection for the input stage (variable-gain amplifier). connect to the circuit board ground plane with a separate low-inductance path (via). 3 v cc supply voltage input for the input stage. bypass with its own 100pf low-inductance capacitor to gnd. 4 v cc supply voltage input for bias circuitry. bypass with its own 100pf low-inductance capacitor and a 1000pf capacitor to gnd, to minimize rf signal coupling into the bias circuits. 5 v cc supply voltage input for the input stage. bypass with its own 22pf low-inductance capacitor to pins 6 and 7. 6, 7, 10 gnd gnd connection for the second-stage amplifier (driver). connect to the circuit board ground plane with a separate low-inductance path (via). 8 v cc supply voltage input for the second stage. bypass with its own 220pf and 1000pf low-inductance capacitors to gnd. 9 v cc supply voltage input for the second stage. connect to pin 8. 11 ramp power ramp pin. connect a capacitor between ramp and ref to provide a gradual linear power-up/down ramp. see detailed description . 12 ref reference voltage for ramp capacitor. the reference is internally set to 1.9v. 13, 14, 17, 18, slug gnd gnd connection for the power stage. solder the slug to the circuit board ground plane. connect pins 13, 14, 17, and 18 to the slug with a straight board trace under the chip. 15 rfout power amplifier output. see typical operating circuit for an example of a matching network, which pro- vides optimal output power at 836mhz. connect to pin 16. 16 rfout power amplifier output. connect to pin 15. 19 shdn shutdown pin. drive shdn low to turn the device off. drive above 2.0v to turn the device on. drive v shdn > 2.0v and v gc < 0.4v for standby mode. 20 gc gain-control pin. apply v gc between 0.6v and 2.3v to control the output power with a monotonic db/v relationship. see the typical operating characteristics for a typical relationship.
MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications 6 _______________________________________________________________________________________ detailed description the MAX2235 power amplifier (pa) operates over a wide frequency range of 800mhz to 1000mhz. the sig- nal path consists of three stages: the input stage, the driver stage, and the power stage. there are matching circuits between the first and second stages, and between the second and third stages. the bias circuits process external commands to control the device? power-up/down and the gain of the pa. input stage the first stage is a variable-gain amplifier with 37db gain-control range. the input transistor acts as a transconductor with constant bias current. gain control is achieved by steering the signal current from the input transistor to the first output matching network (to drive the second stage) or to a separate supply pin. this stage operates in class a and remains on in standby mode to ensure that the vswr at the input does not vary more than 1.5:1 compared with normal operation. the input stage typically requires an external inductor to achieve an optimum input vswr. second stage (driver) the driver produces a signal large enough to drive the power stage into saturation. the driver stage operates in class c and is off during standby. second- and third-stage matching the interstage matching networks provide optimal load- ing and power transfer. the circuits are on-chip to save board space. the bandwidths of the matching net- works allow the pa to operate over a wide frequency range. typical operating circuit 20 19 18 17 8 7 6 5 4 3 2 1 16 15 14 13 9 10 11 12 gnd v cc v cc v cc gnd gnd v cc v cc gnd rfin shdn gnd gnd rfout rfout gnd gnd ref ramp gc 0.068 f 470pf 470pf 1500pf 47pf 1000pf 1000pf 11pf MAX2235 68pf v cc v cc v cc v cc v cc j2 ju2 ju1 sma sma j3 j4 8.2nh * 100pf 100pf 1000pf 1000pf 22pf 100pf 100pf 0.01 f1 f j1 1 2 3 * value of output inductor depends on application.
third stage (power stage) this last stage delivers 30dbm to a 50 ? load. it oper- ates in class e to achieve a high power-added efficien- cy (pae). proper output matching is required for optimal output power. the output of the power stage requires a low-series-resistance pull-up inductor with a minimum current rating of 1.5a. see the typical operating circuit for an example of an output matching circuit. biasing and power control shdn , gc, ramp, and ref are bias and power-control pins. drive shdn below 0.5v to turn off the entire chip, and drive shdn above 2.0v to turn on the device. when shdn is high, a v gc from 0.6v to 2.3v continu- ously controls the gain in the first stage (vga) and the output power. drive gc below 0.4v to put the device in standby mode with only the first stage on. if gc is unconnected and v shdn > 2.0v, the device is set to maximum gain. table 1 summarizes these operating modes. power ramping control a capacitor connected between ramp and ref con- trols the output power rise/fall time to reduce transient noise when shdn turns the device on and off. because the ramp is approximately a raised cosine, this device can be used in direct on/off keying (ook) applications with minimum intersymbol interference. the value of the ramping capacitor is determined from the rise/fall time vs. ramping capacitance curves in the typical operating characteristics . table 1. operating modes board assembly precaution solder the underside metal slug evenly to the board ground plane for optimal performance. fill all vias in the area under the slug. for maximum power gain and sat- urated output power, ensure that the entire slug makes contact with the board ground. MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications _______________________________________________________________________________________ 7 gc shdn >2.0v >0.6v mode on standby >2.0v <0.4v shutdown <0.5v don? care chip information transistor count: 668
MAX2235 +3.6v, 1w autoramping power amplifier for 900mhz applications package information tssop.eps 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. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2001 maxim integrated products printed usa is a registered trademark of maxim integrated products.
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