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19-0586; Rev 1; 2/09
Ultrasound Variable-Gain Amplifier
General Description
The MAX2037 8-channel variable-gain amplifier (VGA) is designed for high linearity, high dynamic range, and low-noise performance targeting ultrasound imaging and Doppler applications. Each amplifier features differential inputs and outputs and a total gain range of typically 42dB. In addition, the VGAs offer very low output-referred noise performance suitable for interfacing with 12-bit ADCs. The MAX2037 VGA is optimized for less than 0.25dB absolute gain error to ensure minimal channel-to-channel ultrasound beamforming focus error. The device's differential outputs are designed to directly drive ultrasound ADCs through an external passive anti-aliasing filter. A switchable clamp is also provided at each amplifier's outputs 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 VOUT = 1.5VP-P and fIN = 5MHz, and an ultrasound-specific* two-tone third-order intermodulation distortion specification of -52dBc at VOUT = 1.5VP-P and fIN = 5MHz. The MAX2037 operates from a +5.0V power supply, consuming only 120mW/channel. The device is available in a 100-pin TQFP package with an exposed pad. Electrical performance is guaranteed over a 0C to +70C temperature range.
Features
8-Channel Configuration High Integration for Ultrasound Imaging Applications Pin Compatible with the MAX2038 Ultrasound VGA Plus CW Doppler Beamformer 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 Pin-for-Pin 10-Bit Compatibility Supported By MAX2035/MAX2036 0.25dB Absolute Gain Error 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 VOUT = 1.5VP-P and fIN = 5MHz Two-Tone Ultrasound-Specific* IMD3 of -52dBc at VOUT = 1.5VP-P and fIN = 5MHz 120mW Consumption Per Channel
*See the Ultrasound-Specific IMD3 Specification in the Applications Information section.
MAX2037
Applications
Ultrasound Imaging Sonar
Functional Diagram
VCC VREF
Ordering Information
PART MAX2037CCQ+D MAX2037CCQ+TD TEMP RANGE 0C to +70C 0C to +70C PIN-PACKAGE 100 TQFP-EP 100 TQFP-EP
MAX2037
VG_CTL+ VG_CTLVG_IN1+ VGA VG_IN1* * * ** ** **
-12.5dB TO +29.5dB VG_CLAMP_MODE 50 VG_OUT1+ VG_OUT1* * *
EP = Exposed pad.
50
* * *
+Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. D = Dry packing.
VG_IN8+ VGA VG_IN8-
50
VG_OUT8+ VG_OUT8-
50 BIAS CIRCUITRY
PD
GND
EXT_RES
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Ultrasound Variable-Gain Amplifier MAX2037
ABSOLUTE MAXIMUM RATINGS
VCC, VREF to GND .................................................-0.3V to +5.5V Any Other Pins to GND...............................-0.3V to (VCC + 0.3V) VGA Differential Input Voltage (VGIN_+ - VGIN_-)...........8.0VP-P Analog Gain-Control Input Differential Voltage (VG_CTL+ - VG_CTL-)...................................................8.0VP-P Continuous Power Dissipation (TA = +70C) 100-Pin TQFP (derated 45.5mW/C above +70C).........................3636.4mW Operating Temperature Range...............................0C to +70C Junction Temperature ......................................................+150C JC (Note 1) .....................................................................+2C/W JA (Note 1) ...................................................................+22C/W Storage Temperature Range .............................-40C to +150C Lead Temperature (soldering, 10s) .................................+300C
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, TA = 0C to +70C, VGND = 0, PD = 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, RL = 1k. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER Supply Voltage Range VCC External Reference Voltage Range Total Power Supply Current VCC Supply Current VREF Current Current Consumption per Amplifier Channel Differential Analog Control Voltage Range Differential Analog Control Common-Mode Voltage Analog Control Input Source/Sink Current LOGIC INPUTS CMOS Input High Voltage CMOS Input Low Voltage VIH VIL 2.0 0.8 V V VCM IVCC IREF Refers to VCC supply current Minimum gain Maximum gain 2.85 SYMBOL VCC VREF (Note 3) Refers to VCC supply current plus VREF current PD = 0 PD =1 CONDTIONS MIN 4.75 4.75 TYP 5 5 204 27 192 12 24 +2 -2 3.0 4.5 3.15 5 MAX 5.25 5.25 231 33 216 15 27 UNITS V V mA mA mA mA VP-P V mA
2
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Ultrasound Variable-Gain Amplifier
AC ELECTRICAL CHARACTERISTICS
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, TA = 0C to +70C, VGND = 0, PD = 0, VG_CLAMP_MODE = 1, fRF = 5MHz, capacitance to GND at each of the VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, RL = 1k. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS Differential output capacitance is 10pF, capacitance to GND at each single-ended output is 60pF, RL = 1k No capacitive load RL = 1k Small Signal Bandwidth Differential Input Resistance Input Effective Capacitance Differential Output Resistance Maximum Gain Minimum Gain Gain Range Absolute Gain Error VGA Gain Response Time Input-Referred Noise TA = +25C, full gain range 0% to 100%, VREF = 5V 40dB gain change to within 1dB final value VG_CTL set for maximum gain, no input signal No input signal Output-Referred Noise VG_CTL set for +10dB of gain VOUT = 1.5VP-P, 1kHz offset f-1.3dB RIN CIN ROUT fRF = 10MHz, each input to ground VOUT = 1.5mVP-P, 3dB bandwidth, gain = 10dB 170 MIN TYP MAX UNITS
MAX2037
Full-Scale Bandwidth
f-1.3dB
VOUT = 1.5VP-P, 1.3dB bandwidth, gain = 10dB
18 MHz
29 30 200 15 100 +29.5 -12.5 42 0.25 1 2 22 55 nV/Hz 1.5 230 MHz pF dB dB dB dB s nV/Hz
VG_CLAMP_MODE = 1, VG_CTL set for +10dB of gain, fRF = 5MHz, VOUT = 1.5VP-P Second Harmonic HD2 VG_CLAMP_MODE = 1, VG_CTL set for +10dB of gain, fRF = 10MHz, VOUT = 1.5VP-P Third-Order Intermodulation Distortion VG_CLT set for +10dB of gain, fRF1 = 5MHz, fRF2 = 5.01MHz, VOUT = 1.5VP-P, VREF = 5V (Note 4) -55
-70 dBc -65
IMD3
-40
-52
dBc
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3
Ultrasound Variable-Gain Amplifier MAX2037
AC ELECTRICAL CHARACTERISTICS (continued)
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, TA = 0C to +70C, VGND = 0, PD = 0, VG_CLAMP_MODE = 1, fRF = 5MHz, capacitance to GND at each of the VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, RL = 1k. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER Channel-to-Channel Crosstalk Maximum Output Voltage at Clamp ON SYMBOL CONDITIONS VOUT = 1VP-P differential, fRF = 10MHz, VG_CTL set for +10dB of gain VG_CLAMP_MODE = 0, VG_CTL set for +20dB of gain, 350mVP-P differential input VG_CLAMP_MODE = 1, VG_CTL set for +20dB of gain, 350mVP-P differential input MIN TYP -80 MAX UNITS dB VP-P differential
2.4
Maximum Output Voltage at Clamp OFF
2.8
VP-P differential
Note 2: Specifications at TA = +25C and TA = +70C are guaranteed by production test. Specifications at TA = 0C are guaranteed by design and characterization. Note 3: Noise performance of the device is dependent on the noise contribution from the supply to VREF. Use a low noise supply for VREF. VCC and VREF can be connected together to share the same supply voltage if the supply for VCC exhibits low noise. Note 4: See the Ultrasound-Specific IMD3 Specification in the Applications Information section.
Typical Operating Characteristics
(Figure 2, VCC = VREF = 4.75V to 5.25V, VGND = 0, PD = 0, VG_CLAMP_MODE = 1, fRF = 5MHz, capacitance to GND at each of the VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, RL = 1k, TA = 0C to +70C. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.)
OVERDRIVE PHASE DELAY vs. FREQUENCY
MAX2037toc01
POWER SUPPLY MODULATION RATIO
MAX2037 toc02
TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. GAIN
VOUT = 1VP-P DIFFERENTIAL -10 -20
MAX2037toc03
5.0 4.5 OVERDRIVE PHASE DELAY (ns) 4.0 3.5 VIN1 = 35mVP-P DIFFERENTIAL VIN2 = 87.5mVP-P DIFFERENTIAL GAIN = 20dB
-40 -50 -60 VOUT = 1.5VP-P DIFFERENTIAL VMOD = 50mVP-P, fCARRIER = 5MHz, GAIN = 10dB
0
PSMR (dBc)
3.0 2.5 2.0 1.5 1.0 0.5 0 0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 FREQUENCY (MHz)
IMD3 (dBc)
-30 f = 10MHz -40 -50 -60 f = 5MHz f = 2MHz -15 -5 5 15 25 35
-70 -80 -90 -100 0 25 50 75 100 125 150 175 200 FREQUENCY (kHz)
-70 -80
GAIN (dB)
4
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Ultrasound Variable-Gain Amplifier
Typical Operating Characteristics (continued)
(Figure 2, VCC = VREF = 4.75V to 5.25V, VGND = 0, PD = 0, VG_CLAMP_MODE = 1, fRF = 5MHz, capacitance to GND at each of the VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, RL = 1k, TA = 0C to +70C. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.)
SECOND HARMONIC DISTORTION vs. GAIN
MAX2037 toc04
MAX2037
THIRD HARMONIC DISTORTION vs. GAIN
-10 -20 -30 HD3 (dBc) f = 12MHz f = 5MHz VOUT = 1VP-P DIFFERENTIAL
MAX2037 toc05
0 -10 -20 -30 HD2 (dBc) -40 -50 -60 -70 -80 -90 -100 -15 -5 5 15 25 f = 5MHz f = 2MHz f = 12MHz VOUT = 1VP-P DIFFERENTIAL
0
-40 -50 -60 -70 -80 -90 -100 f = 2MHz
35
-15
-5
5
15
25
35
GAIN (dB)
GAIN (dB)
OVERLOAD RECOVERY TIME
MAX2037toc06
OVERLOAD RECOVERY TIME
MAX2037toc07
f = 5MHz
DIFFERENTIAL OUTPUT 1.0V/div
f = 5MHz
DIFFERENTIAL OUTPUT 2.0V/div
DIFFERENTIAL INPUT 1.0V/div
OUTPUT 1VP-P TO OVERLOAD AND BACK TO 1VP-P OUTPUT 100mVP-P TO OVERLOAD AND BACK TO 100mVP-P
DIFFERENTIAL INPUT 2.0V/div
400ns/div
400ns/div
CHANNEL-TO-CHANNEL CROSSTALK vs. GAIN
MAX2037 toc08
CHANNEL-TO-CHANNEL CROSSTALK vs. FREQUENCY
-40 -50 CROSSTALK (dB) -60 -70 -80 -90 -100 -110 1 10 FREQUENCY (MHz) 100 VOUT = 1VP-P DIFFERENTIAL GAIN = 10dB, ADJACENT CHANNELS
MAX2037toc09
-60 -65 -70 CROSSTALK (dB) -75 -80 -85 -90 -95 -100 -15 -5 5 15 25 VOUT = 1.5VP-P DIFFERENTIAL f = 10MHz, ADJACENT CHANNELS
-30
35
GAIN (dB)
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5
Ultrasound Variable-Gain Amplifier MAX2037
Typical Operating Characteristics (continued)
(Figure 2, VCC = VREF = 4.75V to 5.25V, VGND = 0, PD = 0, VG_CLAMP_MODE = 1, fRF = 5MHz, capacitance to GND at each of the VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, RL = 1k, TA = 0C to +70C. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.)
OUTPUT-REFERRED NOISE VOLTAGE vs. GAIN
MAX2037toc10
GAIN vs. DIFFERENTIAL ANALOG CONTROL VOLTAGE (VG_CTL)
MAX2037toc11
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
35 30 VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = -2VP-P DIFFERENTIAL
MAX2037toc12
OUTPUT-REFERRED NOISE VOLTAGE (nV/Hz)
50 f = 5MHz 40
35 f = 5MHz 25 15 GAIN (dB) 5 -5
40
GAIN (dB)
30
25 20 15 10
20
10
-15 -25 -15 -5 5 15 25 35 -2.5 -1.5 -0.5 0.5 1.5 2.5 GAIN (dB) VG_CTL (VP-P DIFFERENTIAL)
5 0 0.1 1 10 FREQUENCY (MHz) 100 1000
0
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
MAX2037 toc13
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
MAX2037 toc14
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
5 0 GAIN (dB) -5 -10 -15 -20 -25 -30 VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +1.5VP-P
MAX2037 toc15
30 25 20 GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = -1VP-P DIFFERENTIAL
20 15 10 GAIN (dB) 5 0 -5 -10 -15 -20
10
VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +0.6VP-P DIFFERENTIAL
15 10 5 0 -5 -10 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
MAX2037 toc16
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
MAX2037 toc17
HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT VOLTAGE
-10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 SECOND HARMONIC THIRD HARMONIC VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 10dB
MAX2037 toc18
5 0 -5 GAIN (dB)
VOUT = 1VP-P DIFFERENTIAL VG_CTL = +1.7VP-P DIFFERENTIAL
0 -5 -10 GAIN (dB) -15 -20 -25 -30 -35 -40
0
VOUT = 0.5VP-P DIFFERENTIAL VG_CTL = +2VP-P DIFFERENTIAL
-10 -15 -20 -25 -30 -35 0.1 1 10 FREQUENCY (MHz) 100 1000
0.1
1
10 FREQUENCY (MHz)
100
1000
0
0.5
1.0
1.5
2.0
2.5
3.0
DIFFERENTIAL OUTPUT VOLTAGE (VP-P)
6
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Ultrasound Variable-Gain Amplifier
Typical Operating Characteristics (continued)
(Figure 2, VCC = VREF = 4.75V to 5.25V, VGND = 0, PD = 0, VG_CLAMP_MODE = 1, fRF = 5MHz, capacitance to GND at each of the VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, RL = 1k, TA = 0C to +70C. Typical values are at VCC = VREF = 5V, TA = +25C, unless otherwise noted.)
HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT LOAD RESISTANCE
MAX2037 toc19
MAX2037
HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT LOAD CAPACITANCE
MAX2037 toc20
HARMONIC DISTORTION vs. FREQUENCY
-10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 SECOND HARMONIC THIRD HARMONIC VOUT = 1VP-P DIFFERENTIAL GAIN = 10dB
MAX2037 toc21
-40 -45 HARMONIC DISTORTION (dBc) -50 -55 -60 -65 -70 -75 -80 -85 -90 -95 -100 200 500 800 1100 1400 1700 SECOND HARMONIC VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 10dB THIRD HARMONIC
-40 -45 HARMONIC DISTORTION (dBc) -50 -55 -60 -65 -70 -75 -80 -85 -90 -95 -100 SECOND HARMONIC VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 10dB THIRD HARMONIC
0
2000
5
25
45
65
85
105
0
10
20
30
40
50
DIFFERENTIAL OUTPUT LOAD ()
DIFFERENTIAL OUTPUT LOAD (pF)
FREQUENCY (MHz)
TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. FREQUENCY
MAX2037 toc22
GAIN ERROR HISTOGRAM
45 40 35 % OF UNITS 30 25 20 15 10 SAMPLE SIZE = 202 UNITS, fIN_ = 5MHz, GAIN = 10dB
MAX2037 toc23
0 -10 -20 IMD3 (dBc) -30 -40 -50 -60 -70 0 5 10 15 20 VOUT = 1VP-P DIFFERENTIAL GAIN = 10dB
50
5 25 -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 0.40 GAIN ERROR (dB) 0 FREQUENCY (MHz)
OUTPUT COMMON-MODE OFFSET VOLTAGE vs. GAIN
15 OFFSET VOLTAGE (mV) 10 5 0 -5 -10 -15 -20 -15 -5 5 15 25 35 GAIN (dB)
MAX2037 toc24
DIFFERENTIAL OUTPUT IMPEDANCE MAGNITUDE vs. FREQUENCY
180 160
MAX2037 toc25
20
200
|ZOUT|
140 120 100 80 60 0.1 1 10 100 FREQUENCY (MHz)
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7
Ultrasound Variable-Gain Amplifier MAX2037
Pin Description
PIN 1, 2, 5, 6, 7, 10, 11, 12, 19, 20, 21, 24, 25, 26, 29, 30, 31, 34, 35, 36, 41, 43, 44, 45, 47, 48, 51, 55, 58, 59, 64, 65, 66, 69, 73, 76, 79, 80, 81, 83, 84, 85, 88-92, 96, 97, 98 3 4 8 9 13 14 15 16, 39, 42, 46, 54, 72, 82, 87 17 18 22 23 27 28 32 33 NAME FUNCTION
GND
Ground
VGIN3VGIN3+ VGIN4VGIN4+ EXT_C1 EXT_C2 EXT_C3 VCC VGIN5VGIN5+ VGIN6VGIN6+ VGIN7VGIN7+ VGIN8VGIN8+
VGA Channel 3 Inverting Differential Input VGA Channel 3 Noninverting Differential Input VGA Channel 4 Inverting Differential Input VGA Channel 4 Noninverting Differential Input External Compensation. Connect a 4.7F capacitor to ground. External Compensation. Connect a 4.7F capacitor to ground. External Compensation. Connect a 4.7F capacitor to ground. 5V Power Supply. Bypass each VCC supply to ground with 0.1F capacitors as close to the pins as possible. VGA Channel 5 Inverting Differential Input VGA Channel 5 Noninverting Differential Input VGA Channel 6 Inverting Differential Input VGA Channel 6 Noninverting Differential Input VGA Channel 7 Inverting Differential Input VGA Channel 7 Noninverting Differential Input VGA Channel 8 Inverting Differential Input VGA Channel 8 Noninverting Differential Input 5V Reference Supply. Bypass to GND with a 0.1F capacitor as close to the pins as possible. Note that noise performance of the device is dependent on the noise contribution from the supply to VREF. Use a low noise supply for VREF. VCC and VREF can be connected together to share the same supply voltage if the supply for VCC exhibits low noise. External Resistor. Connect a 7.5k resistor to ground. Power-Down Switch. Drive PD high to set the device in power-down mode. Drive PD low for normal operation. VGA Channel 8 Noninverting Differential Output VGA Channel 8 Inverting Differential Output VGA Channel 7 Noninverting Differential Output VGA Channel 7 Inverting Differential Output VGA Channel 6 Noninverting Differential Output VGA Channel 6 Inverting Differential Output VGA Channel 5 Noninverting Differential Output
37, 93
VREF
38 40 49 50 52 53 56 57 60
EXT_RES PD VGOUT8+ VGOUT8VGOUT7+ VGOUT7VGOUT6+ VGOUT6VGOUT5+
8
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Ultrasound Variable-Gain Amplifier
Pin Description (continued)
PIN 61 62 63 67 68 70 71 74 75 77 78 86 94 95 99 100 -- NAME VGOUT5VG_CTLVG_CTL+ VGOUT4+ VGOUT4VGOUT3+ VGOUT3VGOUT2+ VGOUT2VGOUT1+ VGOUT1VG_CLAMP_MODE VGIN1VGIN1+ VGIN2VGIN2+ EP FUNCTION VGA Channel 5 Inverting Differential Output VGA Analog Gain-Control Inverting Input VGA Analog Gain-Control Noninverting Input VGA Channel 4 Noninverting Differential Output VGA Channel 4 Inverting Differential Output VGA Channel 3 Noninverting Differential Output VGA Channel 3 Inverting Differential Output VGA Channel 2 Noninverting Differential Output VGA Channel 2 Inverting Differential Output VGA Channel 1 Noninverting Differential Output VGA Channel 1 Inverting Differential Output VGA Clamp Mode Enable. Drive VG_CLAMP_MODE low to enable VGA clamping. VGA output will be clamped at typically 2.4VP-P differential. Drive VG_CLAMP_MODE high to disable VGA clamp mode. VGA Channel 1 Inverting Differential Input VGA Channel 1 Noninverting Differential Input VGA Channel 2 Inverting Differential Input VGA Channel 2 Noninverting Differential Input Exposed pad. Internally connected to GND. Solder the exposed pad to the ground plane using multiple vias.
MAX2037
Detailed Description
The MAX2037's VGAs are optimized for high linearity, high dynamic range, and low output noise performance, making this component ideal for ultrasoundimaging applications. The VGA paths also exhibit a channel-to-channel crosstalk of -80dB at 10MHz and an absolute gain error of less than 0.25dB 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_-) that are ideal for directly interfacing to the MAX2034 quad LNA. See the Functional Diagram for details. The VGA has an adjustable gain range from -12.5dB to +29.5dB, achieving a total dynamic range of typically 42dB. The VGA gain can be adjusted with the differential gain-control input VG_CTL+ and VG_CTL-. Set the differential gain-control input voltage at -2V for maximum gain and +2V for minimum gain. The differential analog control common-mode voltage is typically 3.0V.
VGA Clamp
A clamp is provided to limit the VGA output signals to avoid overdriving the ADC or to prevent ADC saturation. Set VG_CLAMP_MODE low to clamp the VGA differential outputs at 2.4VP-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 transmit-related overload.
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9
Ultrasound Variable-Gain Amplifier MAX2037
Applications Information
External Compensation
External compensation is required for bypassing internal biasing circuitry. Connect, as close as possible, individual 4.7F capacitors from each pin EXT_C1, EXT_C2, and EXT_C3 (pin 13, 14, 15) to ground.
Board Layout
The pin configuration of the MAX2037 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 MAX2037's TQFP-EP package provides a low thermal-resistance path to the die. It is important that the PCB on which the MAX2037 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.
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 resistor from EXT_RES (pin 38) to ground.
Analog Input and Output Coupling
In typical applications, the MAX2037 is being driven from a low-noise amplifier (such as the MAX2034) and is typically driving a discrete differential anti-alias filter into an ADC (such as the MAX1436 octal ADC). The differential input impedance of the MAX2037 is typically 200. The differential outputs are capable of driving a differential load resistance of 1000. The output impedance is 100 differential. The differential outputs have a common-mode bias of approximately 3.0V. ACcouple these differential outputs if the next stage has a different common-mode input range.
-25dB
ULTRASOUND IMD3
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, f 1 represents reflections from tissue and f 2 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.
f1 - (f2 - f1)
f1
f2
f2 + (f2 - f1)
Figure 1. Ultrasound IMD3 Measurement Technique
10
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Ultrasound Variable-Gain Amplifier MAX2037
ZIN CONTROL D2, D1, D0 SINGLE CHANNEL
MAX2034
SINGLE CHANNEL +V VG_CTL+ VG_CTL18nF 100nF 100nF VGIN_+ VGIN_100nF VGA 50 50 100nF VG_OUT_+ VG_OUT_100nF TO A SINGLE CHANNEL OF
MAX2037
VIN
MAX1436 ADC
100nF -V
Figure 2. Typical Per-Channel Ultrasound-Imaging Application
Pin Configuration
TOP VIEW VG_CLAMP_MODE GND GND GND GND VGOUT1VGOUT1+ GND 81 80 79 78 76 77
GND VGIN1+ VGIN1VREF
VGIN2+
VGIN2GND GND
GND GND
GND GND
100 99 98
97
96
95
94
93
92
91
90
89
87
GND VCC
86
85
84
83
+
GND GND VGIN3VGIN3+ GND GND GND VGIN4VGIN4+ GND GND GND EXT_C1 EXT_C2 EXT_C3 VCC VGIN5VGIN5+ GND GND GND VGIN6VGIN6+ GND GND
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52
82
88
GND GND VCC
VGOUT2VGOUT2+ GND VCC VGOUT3VGOUT3+ GND VGOUT4VGOUT4+ GND GND GND VG_CTL+ VG_CTLVGOUT5VGOUT5+ GND GND VGOUT6VGOUT6+ GND VCC VGOUT7VGOUT7+ GND
MAX2037
*EP
51
26 27 28
29
31
32 33 34 35
36
37 38 39
40
41
42
43
45
46
47 48
49
GND VGIN7-
VGIN7+ GND GND
*EP = EXPOSED PAD
TQFP (14mm x 14mm)
______________________________________________________________________________________
GND GND VGOUT8+ VGOUT8-
GND VGIN8VGIN8+ GND
GND GND VREF
EXT_RES VCC
PD
GND VCC
GND GND GND VCC
50
30
44
11
Ultrasound Variable-Gain Amplifier MAX2037
Chip Information
PROCESS: Silicon Complementary Bipolar
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 100 TQFP-EP PACKAGE CODE C100E+3 DOCUMENT NO. 21-0085
12
______________________________________________________________________________________
Ultrasound Variable-Gain Amplifier
Revision History
REVISION NUMBER 0 1 REVISION DATE 10/06 2/09 Initial release Updated various sections DESCRIPTION PAGES CHANGED -- 1-7, 9, 12
MAX2037
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) 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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