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19-3969; Rev 1; 3/07
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
General Description
The MAX2034 four-channel, low-power, ultra-low-noise preamplifier is designed for ultrasound and medical instrumentation applications. Each low-noise amplifier has a single-ended input, differential output, a highly accurate 19dB fixed gain, and a wide -3dB bandwidth of 70MHz. The high-gain accuracy of the amplifier allows for exceptional channel-to-channel gain matching, which is necessary for high-performance ultrasound-imaging applications. The MAX2034 also includes an on-chip programmable input impedance feature that allows the device to be compatible with a variety of common source impedances ranging from 50 to 1k. The input impedance of each amplifier uses a feedback topology for active impedance matching. The active input impedance matching feature achieves an exceptionally low 2.2dB noise figure with a source and input impedance of 200. The MAX2034 has excellent dynamic and linearity performance characteristics optimized for all ultrasoundimaging modalities including second harmonic 2D imaging and continuous wave Doppler. The device achieves a second harmonic distortion of -68dBc at VOUT = 1VP-P and fIN = 5MHz, and an ultrasound-specific* two-tone third-order intermodulation distortion performance of -55dBc at VOUT = 1VP-P and fIN = 5MHz. The MAX2034 is also optimized for quick overload recovery for operation under the large input signal conditions typically found in ultrasound input-buffer imaging applications. The MAX2034 is available in a 48-pin thin QFN package with an exposed paddle. Electrical performance is guaranteed over a 0C to +70C temperature range.
Features
High-Level Integration of 4 Channels Digitally Programmable Input Impedance (RIN) of 50, 100, 200, and 1k Integrated Input Clamp Integrated Input-Damping Capacitor Ultra-Low 2.2dB Noise Figure at RS = RIN = 200 70MHz, -3dB Bandwidth Low 58mW/Channel Power Dissipation HD2 of -68dBc at VOUT = 1VP-P and fIN = 5MHz for Exceptional Second Harmonic Imaging Performance Two-Tone Ultrasound-Specific* IMD3 of -55dBc at VOUT = 1VP-P and fIN = 5MHz for Exceptional PW/CW Doppler Performance Quick Large-Signal Overload Recovery Single +5V Supply Operation Sleep Mode
Applications
Ultrasound Imaging Sonar Signal Amplification
Pin Configuration
OUT1+ OUT2+ OUT3+ OUT1OUT2GND GND GND VCC VCC VCC
TOP VIEW
36 35 34 33 32 31 30 29 28 27 26 25 GND 37 38 39 40 41 42 43 44 45 46 47 48 1 INC1 2 INB1 3 ZF2 4 IN2 5 INC2 6 INB2 7 ZF3 8 IN3 9 INC3 10 11 12 ZF4 INB3 IN4 24 23 22 21 20 19 OUT4+ OUT4GND GND VCC D0 D1 VCC VCC GND INB4 INC4
Ordering Information
PART MAX2034CTM+ MAX2034CTM TEMP RANGE 0C to +70C 0C to +70C PINPACKAGE PKG CODE
VCC GND GND VCC D2 PD VCC VCC GND ZF1 IN1
48 Thin QFN-EP** T4877-4 (7mm x 7mm) 48 Thin QFN-EP** T4877-4 (7mm x 7mm) 48 Thin QFN-EP** T4877-4 (7mm x 7mm) 48 Thin QFN-EP** T4877-4 (7mm x 7mm)
MAX2034
OUT3-
18 17 16 15 14 13
MAX2034CTM+T 0C to +70C MAX2034CTM-T 0C to +70C
**EP = Exposed paddle. +Denotes lead-free package. T = Tape-and-reel package. *See the Ultrasound-Specific IMD3 Specification in the Applications Information section.
THIN QFN
Typical Application Circuit appears at end of data sheet. 1
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +5.5V Any Other Pins to GND...............................-0.3V to (VCC + 0.3V) IN_ to INB_ ..................................................................-2V to +2V INC_ to GND .....................................................-24mA to +24mA Continuous Power Dissipation (TA = +70C) 48-Pin TQFN (derated 40mW/C above +70C) ........3200mW Operating Temperature Range...............................0C to +70C Junction Temperature ......................................................+150C JC ...................................................................................0.8C/W JA ....................................................................................25C/W Storage Temperature Range .............................-40C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(MAX2034 Typical Application Circuit, VCC = +4.75V to +5.25V, no input signal applied between IN1-IN4 and GND, TA = 0C to +70C. Typical values are at VCC = +5.0V and TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Supply Voltage SYMBOL VCC ICC ICC,PD LOGIC INPUTS (PD, D2, D1, D0) Input High Voltage Input Low Voltage Input Current with Logic-High Input Current with Logic-Low VIH VIL IIH IIL 4.0 1.0 1 1 V V A A Normal mode (PD = 0), no signals applied, see the Typical Operating Characteristics for ICC as a function of input signal Sleep mode (PD = 1), VIN_ = 112mVP-P at 5MHz CONDITIONS MIN 4.75 TYP 5.0 46.5 0.8 MAX 5.25 54.5 4 UNITS V
Total Supply Current
mA
AC ELECTRICAL CHARACTERISTICS
(MAX2034 Typical Application Circuit, VCC = +4.75V to +5.25V, source impedance RS = 200, PD = 0, D2/D1/D0 = 0/1/0 (RIN = 200), signal AC-coupled to IN_, INB_ is AC grounded, VOUT is the differential output between OUT_+ and OUT_-, fIN_ = 5MHz, RL = 200 between the differential outputs, CL = 20pF from each output to ground, TA = 0C to +70C. Typical values are at VCC = 5.0V and TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL D2/D1/D0 = 0/0/0 Input Resistance RIN D2/D1/D0 = 0/0/1 D2/D1/D0 = 0/1/0 D2/D1/D0 = 0/1/1 Typical Input Resistance Variation from Nominal Programmed Input Capacitance Gain Part-to-Part Gain Variation from Nominal -3dB Small-Signal Gain Bandwidth Slew Rate f-3dB CIN AV (OUT_+ - OUT_-) / IN_ TA = +25oC, RL = 200 10% D2/D1/D0 = 0/0/0, (50 input impedance), VOUT = 0.2VP-P 0 CONDITIONS MIN TYP 53 105 206 870 1 40 19 0.1 0.5 % pF dB dB MAX UNITS
70 280
MHz V/s
2
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Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2034 Typical Application Circuit, VCC = +4.75V to +5.25V, source impedance RS = 200, PD = 0, D2/D1/D0 = 0/1/0 (RIN = 200), signal AC-coupled to IN_, INB_ is AC grounded, VOUT is the differential output between OUT_+ and OUT_-, fIN_ = 5MHz, RL = 200 between the differential outputs, CL = 20pF from each output to ground, TA = 0C to +70C. Typical values are at VCC = 5.0V and TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL RS = RIN = 50 Noise Figure NF RS = RIN = 100 RS = RIN = 200 RS = RIN = 1000 Input-Referred Noise Voltage Input-Referred Noise Current Second Harmonic Third Harmonic HD2 HD3 D2 = 1 (high input impedance), fIN_ = 5MHz D2 = 1 (high input impedance), fIN_ = 5MHz fIN_ = 5MHz, VOUT = 1VP-P differential fIN_ = 10MHz, VOUT = 1VP-P differential fIN_ = 5MHz, VOUT = 1VP-P differential fIN_ = 10MHz, VOUT = 1VP-P differential 4.99MHz tone relative to the second tone at 5.01MHz, which is 25dB lower than the first tone at 5.00MHz, VOUT = 1VP-P differential IMD3 7.49MHz tone relative to the second tone at 7.51MHz, which is 25dB lower than the first tone at 7.50MHz, VOUT = 1VP-P differential Differential output Gain at VIN_ = 112mVP-P relative to gain at VIN_ = 550mVP-P Single-ended Phase difference between channels with VIN_ = 195mV peak (-3dB full scale), fIN_ = 10MHz fIN_ = 10MHz, VOUT = 1VP-P, adjacent channels Supply current settles to 90% of nominal sleepmode current ICC,PD VOUT settles to 90% of final 1VP-P output 50 -52 -45 -50 CONDITIONS MIN TYP 4.1 2.9 2.2 1.4 0.87 2.1 -68 -66 -50 -44 -55 dBc nV/Hz pA/Hz dBc dBc dB MAX UNITS
MAX2034
Two-Tone Intermodulation Distortion (Note 2)
Maximum Output Signal Amplitude Gain Compression Output Common-Mode Level Output Impedance Phase Matching Between Channels Channel-to-Channel Crosstalk Switch Time from Normal to Sleep Mode Switch Time from Sleep to Normal Mode
4.4 0.5 2.45 5.3 1.5 66 0.3 0.3 3
VP-P dB V deg dB ms ms
Note 1: Min and max limits at TA = +25C and +70C are guaranteed by design, characterization, and/or production test. Note 2: See the Ultrasound-Specific IMD3 Specification in the Applications Information section.
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3
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
Typical Operating Characteristics
(MAX2034 Typical Application Circuit, VCC = +4.75V to +5.25V, source impedance RS = 200, PD = 0, D2/D1/D0 = 0/1/0 (RIN = 200), signal AC-coupled to IN_, INB_ is AC grounded, VOUT is the differential output between OUT_+ and OUT_-, fIN_ = 5MHz, RL = 200 between the differential outputs, CL = 20pF from each output to ground, TA = 0C to +70C, unless otherwise specified.)
SMALL-SIGNAL BANDWIDTH vs. FREQUENCY
MAX2034 toc01
SMALL-SIGNAL BANDWIDTH vs. FREQUENCY
MAX2034 toc02
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
VIN_ = 500mVP-P, RIN = 200
MAX2034 toc03
25 20 15 GAIN (dB) VIN_ = 112mVP-P, RIN = 200
25 20 15 GAIN (dB) 10 5 0 -5 VIN = 112mVP-P RIN = 50
25 20 15 GAIN (dB) 10 5 0 -5
10 5 0 -5 0.1 1 10 FREQUENCY (MHz) 100 1000
0.1
1
10 FREQUENCY (MHz)
100
1000
0.1
1
10 FREQUENCY (MHz)
100
1000
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
MAX2034 toc04
COMPLEX INPUT IMPEDANCE MAGNITUDE vs. FREQUENCY
MAX2034 toc05
COMPLEX INPUT IMPEDANCE MAGNITUDE vs. FREQUENCY
130 120 110 D2/D1/D0 = 0/0/1 RIN = 100
MAX2034 toc06
25 20 15 GAIN (dB) VIN = 500mVP-P RIN = 50
70 65 60 55 D2/D1/D0 = 0/0/0 RIN = 50
140
IZINI
IZINI
10 5 0 -5 0.1 1 10 FREQUENCY (MHz) 100 1000
50 45 40 35 30 0 10 20 30 40 50 FREQUENCY (MHz)
100 90 80 70 60 0 5 10 15 20 25 30 FREQUENCY (MHz)
MAX2034 toc07
250 225
D2/D1/D0 = 0/1/0 RIN = 200
1000 850
HARMONIC DISTORTION (dBc)
-30 -40 -50 -60 -70
VOUT = 1VP-P DIFFERENTIAL RL = 200
IZINI
200 175
IZINI
700 550 400
THIRD HARMONIC
150 250 125 100 100 0 4 8 12 16 20 FREQUENCY (MHz) 0 4 8 12 16 20
SECOND HARMONIC
-80 0 5 10 15 20 25 30 FREQUENCY (MHz)
FREQUENCY (MHz)
4
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MAX2034 toc09
275
D2/D1/D0 = 0/1/1 RIN = 1k
MAX2034 toc08
COMPLEX INPUT IMPEDANCE MAGNITUDE vs. FREQUENCY
COMPLEX INPUT IMPEDANCE MAGNITUDE vs. FREQUENCY
1150 -20
HARMONIC DISTORTION vs. FREQUENCY
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
Typical Operating Characteristics (continued)
(MAX2034 Typical Application Circuit, VCC = +4.75V to +5.25V, source impedance RS = 200, PD = 0, D2/D1/D0 = 0/1/0 (RIN = 200), signal AC-coupled to IN_, INB_ is AC grounded, VOUT is the differential output between OUT_+ and OUT_-, fIN_ = 5MHz, RL = 200 between the differential outputs, CL = 20pF from each output to ground, TA = 0C to +70C, unless otherwise specified.)
TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. FREQUENCY
MAX2034 toc10
LARGE-SIGNAL NOISE FIGURE vs. OFFSET FREQUENCY
RIN = 200 RL = 200 fIN_ = 5MHz
MAX2034 toc11
0 -10 -20 IMD3 (dBc) -30 -40 -50 -60 -70 0
LARGE-SIGNAL NOISE FIGURE (dB)
VOUT = 1VP-P DIFFERENTIAL RL = 200
6 5 4 3 2 VIN = 112mVP-P 1 0 SMALL-SIGNAL NOISE FIGURE
VIN = 300mVP-P VIN = 200mVP-P
5
10
15
20
25
30
0.1
1
10
100
FREQUENCY (MHz)
OFFSET FREQUENCY (kHz)
GAIN-ERROR HISTOGRAM
MAX2034 toc12
CHANNEL-TO-CHANNEL CROSSTALK vs. FREQUENCY
-40 -50 CROSSTALK (dB) -60 -70 -80 -90 -100 VOUT = 1VP-P DIFFERENTIAL RL = 200 ADJACENT CHANNELS
MAX2034 toc13
50 45 40 35 % OF UNITS 30 25 20 15 10 5 0
-30
SAMPLE SIZE = 243 UNITS fIN_ = 5MHz, VIN = 112mVP-P
-0.20
-0.16
-0.12
-0.08
-0.04
0.02
0.06
0.10
0.14
0.18
1
10 FREQUENCY (MHz)
100
GAIN ERROR (dB)
SUPPLY CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX2034 toc14
LARGE-SIGNAL RECOVERY
MAX2034 toc15
130
ALL CHANNELS ACTIVE
fIN_ = 5MHz
110 SUPPLY CURRENT (mA)
90
INPUT IN_ 500mV/div RL = 200 DIFFERENTIAL OUTPUT OUT_+ - OUT_2.0V/div
70 NO LOAD
50
30 0 1 2 3 4 400ns/div DIFFERENTIAL OUTPUT VOLTAGE (VP-P)
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5
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
Typical Operating Characteristics (continued)
(MAX2034 Typical Application Circuit, VCC = +4.75V to +5.25V, source impedance RS = 200, PD = 0, D2/D1/D0 = 0/1/0 (RIN = 200), signal AC-coupled to IN_, INB_ is AC grounded, VOUT is the differential output between OUT_+ and OUT_-, fIN_ = 5MHz, RL = 200 between the differential outputs, CL = 20pF from each output to ground, TA = 0C to +70C, unless otherwise specified.)
CLAMP SYMMETRY UNDER TRANSMIT RECOVERY
MAX2034 toc17
LARGE-SIGNAL RECOVERY
MAX2034 toc16
fIN_ = 10MHz
fIN_ = 5MHz SINGLE-ENDED OUTPUT OUT_+ 1V/div
INPUT IN_ 500mV/div DIFFERENTIAL OUTPUT OUT_+ - OUT_2.0V/div
SINGLE-ENDED OUTPUT OUT_1V/div
400ns/div
200ns/div
Pin Description
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15, 21, 22, 25, 26, 33, 37, 39, 40, 46 16, 17, 20, 27, 30, 34, 38, 41, 44, 45 NAME INC1 INB1 ZF2 IN2 INC2 INB2 ZF3 IN3 INC3 INB3 ZF4 IN4 INC4 INB4 GND FUNCTION Channel 1 Analog Input Clamp. Input port to the integrated clamping diodes. Channel 1 Analog Bypass Input. Connect a capacitor to GND as close as possible to the pin. Channel 2 Active Impedance-Matching Port. AC-couple to the source circuit with a capacitor. Channel 2 LNA Analog Input. Single-ended input for channel 2 amplifier. Connect the analog input to the source circuit through a series capacitor. Channel 2 Analog Input Clamp. Input port to the integrated clamping diodes. Channel 2 Analog Bypass Input. Connect a capacitor to GND as close as possible to the pin. Channel 3 Active Impedance-Matching Port. AC-couple to the source circuit with a capacitor. Channel 3 LNA Analog Input. Single-ended input for channel 3 amplifier. Connect the analog input to the source circuit through a series capacitor. Channel 3 Analog Input Clamp. Input port to the integrated clamping diodes. Channel 3 Analog Bypass Input. Connect a capacitor to GND as close as possible to the pin. Channel 4 Active Impedance-Matching Port. AC-couple to the source circuit with a capacitor. Channel 4 LNA Analog Input. Single-ended input for channel 4 amplifier. Connect the analog input to the source circuit through a series capacitor. Channel 4 Analog Input Clamp. Input port to the integrated clamping diodes. Channel 4 Analog Bypass Input. Connect a capacitor to GND as close as possible to the pin. Ground
VCC
5V Power Supply. Supply for the four LNAs. Bypass each VCC supply with a 100nF capacitor as close as possible to the pin.
6
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Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance
Pin Description (continued)
PIN 18, 19, 42 23 24 28 29 31 32 35 36 43 47 48 EP NAME D1, D0, D2 OUT4OUT4+ OUT3OUT3+ OUT2OUT2+ OUT1OUT1+ PD ZF1 IN1 GND FUNCTION Digitally Programmable Inputs. Programs the input impedance of each amplifier. See Table 1 on input impedance programming information. Channel 4 LNA Analog Inverting Output Channel 4 LNA Analog Noninverting Output Channel 3 LNA Analog Inverting Output Channel 3 LNA Analog Noninverting Output Channel 2 LNA Analog Inverting Output Channel 2 LNA Analog Noninverting Output Channel 1 LNA Analog Inverting Output Channel 1 LNA Analog Noninverting Output Power-Down. Drive PD high to put the device in sleep mode. Drive PD low for normal mode. Channel 1 Active Impedance-Matching Port. AC-couple to the source circuit with a capacitor. Channel 1 LNA Analog Input. Single-ended input for channel 1 amplifier. Connect the analog input to the source circuit through a series capacitor. Exposed Paddle. Solder the exposed paddle to the ground plane using multiple vias.
MAX2034
Detailed Description
The MAX2034 is a four-channel, ultra-low-noise preamplifier. Each amplifier features single-ended inputs, differential outputs, and provides an accurate fixed gain of 19dB with a wide -3dB bandwidth of 70MHz. The highgain accuracy of the amplifier allows for exceptional channel-to-channel gain matching, which is necessary for high-performance ultrasound-imaging applications. The device has an exceptionally low noise figure, making it ideal for use in ultrasound front-end designs. Noise figure is typically 2.2dB for a source impedance and programmed input impedance of 200. The MAX2034 is optimized for excellent dynamic range and linearity performance characteristics, making it ideal for ultrasound-imaging modalities including second harmonic 2D imaging and continuous wave Doppler. The device achieves an HD2 of -68dBc at VOUT = 1VP-P and fIN_ = 5MHz, and an ultrasound-specific two-tone IMD3 performance of -55dBc at V OUT = 1VP-P and f IN_ = 5MHz. See the Ultrasound-Specific IMD3 Specification in the Applications Information section.
amplifier, A, being defined with a differential output. For common input impedances, the internal digitally programmed impedances can be used (see Table 1). For other input impedances, program the impedance for external resistor operation, and then use an externally supplied resistor to set the input impedance according to the above formula. The gain and input impedance of the MAX2034 vs. frequency are shown in the Typical Operating Characteristics. Both gain and input impedance are well behaved, with no peaking characteristics. This allows the device to be used with a variety of input networks, with no requirement for series ferrite beads or shunt capacitors for stability control.
Table 1. Digitally Programmable Input Impedance
D2 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 Defined by external resistor RIN () 50 100 200 1k
Active Impedance Matching
To provide exceptional noise-figure characteristics, the input impedance of each amplifier uses a feedback topology for active impedance matching. A feedback resistor of the value (1 + (A / 2)) x RS is added between the inverting output of the amplifier to the input. The input impedance is the feedback resistor, ZF, divided by 1 + (A / 2). The factor of two is due to the gain of the
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7
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
Functional Diagram
D2/D1/D0
Digitally Programmable Input Impedance
The MAX2034 features an on-chip digitally programmable input impedance, which makes the part compatible with a variety of source impedances ranging from 50 to 1k. The input impedance can be programmed for 50, 100, 200, or 1k through the digital inputs D2, D1, and D0. See Table 1 for programming details. In addition to these fixed values, virtually any other input impedance can be supported by using an off-chip external feedback resistor, RF. To utilize this feature, set D2, D1, and D0 to any of the four external resistor-controlled states shown in Table 1. The value of the off-chip feedback resistor can be determined by using the following relationship: RF = (1 + (A / 2)) x RS where RS is the source impedance, and A is the gain of the amplifier (A = 9) defined with a differential output.
PD
ZF1
IN1 INC1
OUT1-
OUT1+
INB1
MAX2034
Noise Figure
ZF2
IN2 INC2
OUT2-
OUT2+
INB2
The MAX2034 is designed to provide maximum input sensitivity with its exceptionally low noise figure. The input active devices are selected for very low equivalent input noise voltage and current, and they have been optimized for source impedances from 50 to 1000. Additionally, the noise contribution of the matching resistor is effectively divided by 1 + (A / 2). Using this scheme, typical noise figure of the amplifier is approximately 2.2dB for RIN = RS = 200. Table 2 illustrates the noise figure for other input impedances.
ZF3
Table 2. Noise Figure vs. Source and Input Impedances
Rs () RIN () 50 100 200 1000 NF (dB) 4.1 2.9 2.2 1.4
OUT3-
IN3 INC3
50 100 200 1000
OUT3+
INB3
Input Clamp
ZF4
IN4 INC4
OUT4-
OUT4+
INB4
The MAX2034 includes configurable integrated inputclamping diodes. The diodes are clamped to ground at 275mV. The input-clamping diodes can be used to prevent large transmit signals from overdriving the inputs of the amplifiers. Overdriving the inputs could possibly place charge on the input-coupling capacitor, causing longer transmit overload recovery times. Input signals are AC-coupled to the single-ended inputs IN1-IN4, but are clamped with the INC1-INC4 inputs. See the Typical Application Circuit. If external clamping devices are preferred, simply leave INC1-INC4 unconnected.
8
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Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance
Integrated Input Damping Capacitor
At high frequencies, gain peaking can occur due to an active input termination becoming less effective when the gain rolls off. Although an external shunting capacitor can be used to mitigate this effect, different input impedance modes require different capacitor values. The MAX2034 integrates a damping capacitor for each of the four programmed input impedance modes. When the input impedance is programmed by applying the appropriate D2/D1/D0, an optimal capacitor value is also chosen for the particular input impedance mode, eliminating the need for external capacitors. The Typical Application Circuit illustrates these coupling capacitors. If a ground-referenced current-limiting stage precedes the MAX2034 inputs, its output can be connected to the integrated clamping diodes on pins INC1-INC4 to facilitate very rapid recovery from transient overloads associated with transmitter operation in ultrasound applications.
MAX2034
Analog Output Coupling
The differential outputs of the MAX2034 are capable of driving a differential load impedance of 200 or greater. The differential output has a common-mode bias of approximately 2.45V. AC-couple these differential outputs if the next stage has a different commonmode input range.
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. Internal signal clipping is symmetrical. Input overloads can be prevented with the input-clamping diodes. See the Typical Operating Characteristics that illustrate the rapid recovery time from a transmitrelated overload.
Board Layout
The pin configuration of the MAX2034 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 paddle (EP) of the MAX2034's thin QFNEP package provides a low thermal-resistance path to the die. It is important that the PC board on which the MAX2034 is mounted be designed to conduct heat from the EP. In addition, provide the EP with a lowinductance path to electrical ground. The EP MUST be soldered to a ground plane on the PC board, either directly or through an array of plated via holes.
Sleep Mode
The sleep mode function allows the MAX2034 to be configured in a low-power state when the amplifiers are not being used. In sleep mode, all amplifiers are powered down, the total supply current of the device reduces to 0.8mA, and the input impedance of each amplifier is set at high impedance. Drive the PD input high to activate sleep mode. For normal operation, drive the PD input low.
Applications Information
Analog Input Coupling
AC-couple to ground the analog bypass input by connecting a 0.1F capacitor at the INB1-INB4 input to GND (0.1F recommended). Since the amplifiers are designed with a differential input stage, bypassing the INB1-INB4 inputs configures the MAX2034 for singleended inputs at IN1-IN4. Connect the IN1-IN4 inputs to their source circuits through 0.1F series capacitors. Connect the feedback ports ZF1-ZF4 to the source circuits through 0.018F capacitors. (These capacitors will be 1/(5.5) as large as the input-coupling capacitors. This equalizes the highpass filter characteristic of both the input and feedback input ports, due to the feedback resistance related by a factor of 1/(5.5) to the input impedance.) Note that the active input circuitry of the MAX2034 is stable, and does not require external ferrite beads or shunt capacitors to achieve high-frequency stability.
-25dB
ULTRASOUND IMD3
F1 - (F2 - F1)
F1
F2
F2 + (F2 - F1)
Figure 1. Ultrasound IMD3 Measurement Technique _______________________________________________________________________________________ 9
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
D2/D1/D0
PD +V ZF_
18nF 100nF IN_ 100nF OUT_100nF INC_ ONE CHANNEL INB_ -V 100nF OUT_+
MAX2034
Figure 2. Typical Single-Channel Ultrasound Application Circuit
Ultrasound-Specific IMD3 Specification
Unlike typical communications specs, the two input tones are not equal in magnitude for the ultrasoundspecific IMD3 two-tone specification. In this measurement, F1 represents reflections from tissue and F2 represents reflections from blood. The latter reflections 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 (F1 - (F2 F1)) presents itself as an undesired Doppler error signal in ultrasound applications. See Figure 1.
10
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Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
Typical 200 Application Circuit
+5V 100nF 18nF 100nF
GND
GND
GND
100nF INC1 RS = 200 100nF 18nF 100nF RS = 200 100nF 18nF 100nF RS = 200 100nF 18nF 100nF RS = 200
48
47
46
45
44
43
42
41
40
39
38
GND 37
VCC
VCC
VCC
VCC
ZF1
IN1
PD
D2
1
INB1 ZF2 IN2 INC2 INB2 ZF3 IN3 INC3 INB3 ZF4 IN4
36 35 34 33 32 31
OUT1+ OUT1VCC GND OUT2+ OUT2VCC OUT3+ OUT3VCC GND GND
100nF 100nF
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
OUT4INC4 INB4 GND GND OUT4+ GND VCC D1 VCC D0 VCC EXPOSED PADDLE
100nF 100nF 100nF
MAX2034
30 29 28 27 26 25
100nF 100nF
100nF
100nF
100nF 100nF
100nF 100nF +5V +5V 100nF
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11
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance MAX2034
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
E E/2
DETAIL A
(NE-1) X e
k e D/2
D
(ND-1) X e
C L
D2
D2/2
b L E2/2 DETAIL B e L k
C L
E2
C L
C L
L1
L e e
L
A1
A2
A
PACKAGE OUTLINE 32, 44, 48, 56L THIN QFN, 7x7x0.8mm
21-0144
E
1
2
12
______________________________________________________________________________________
32, 44, 48L QFN.EPS
Quad-Channel, Ultra-Low-Noise Amplifier with Digitally Programmable Input Impedance
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
MAX2034
PACKAGE OUTLINE 32, 44, 48, 56L THIN QFN, 7x7x0.8mm
21-0144
E
2
2
Revision History
Pages changed at Rev 1: 1, 3, 4, 11, 12
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit 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 ____________________ 13 (c) 2007 Maxim Integrated Products
Springer
is a registered trademark of Maxim Integrated Products, Inc.

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