19-0586; Rev 1; 2/09 Ultrasound Variable-Gain Amplifier Features 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 0°C to +70°C temperature range. ♦ 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 Applications Ultrasound Imaging Sonar *See the Ultrasound-Specific IMD3 Specification in the Applications Information section. Ordering Information Functional Diagram VCC VREF PART MAX2037 VG_CTL+ -12.5dB TO +29.5dB VG_CTL- VG_CLAMP_MODE 50Ω VG_IN1+ VG_OUT1+ VGA VG_IN1• • • 50Ω • • • • • • • • • 50Ω VG_IN8+ VG_OUT1• • • TEMP RANGE MAX2037CCQ+D 0°C to +70°C MAX2037CCQ+TD 0°C to +70°C PIN-PACKAGE 100 TQFP-EP† 100 TQFP-EP† †EP = Exposed pad. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. D = Dry packing. VG_OUT8+ VGA VG_IN8- 50Ω VG_OUT8- BIAS CIRCUITRY PD GND EXT_RES ________________________________________________________________ Maxim Integrated Products 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. 1 MAX2037 General Description MAX2037 Ultrasound Variable-Gain Amplifier 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 = +70°C) 100-Pin TQFP (derated 45.5mW/°C above +70°C).........................3636.4mW Operating Temperature Range...............................0°C to +70°C Junction Temperature ......................................................+150°C θJC (Note 1) .....................................................................+2°C/W θJA (Note 1) ...................................................................+22°C/W Storage Temperature Range .............................-40°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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 = 0°C to +70°C, 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 = 1kΩ. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL Supply Voltage Range VCC VCC External Reference Voltage Range VREF CONDTIONS TYP MAX UNITS 4.75 5 5.25 V 4.75 5 5.25 V PD = 0 204 231 PD =1 27 33 (Note 3) Refers to VCC supply current plus VREF current Total Power Supply Current MIN mA VCC Supply Current IVCC 192 216 mA VREF Current IREF 12 15 mA Refers to VCC supply current 24 27 mA Minimum gain +2 Maximum gain -2 Current Consumption per Amplifier Channel Differential Analog Control Voltage Range Differential Analog Control Common-Mode Voltage VCM 2.85 Analog Control Input Source/Sink Current VP-P 3.0 3.15 V 4.5 5 mA LOGIC INPUTS CMOS Input High Voltage VIH CMOS Input Low Voltage VIL 2 2.0 _______________________________________________________________________________________ V 0.8 V Ultrasound Variable-Gain Amplifier (Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, TA = 0°C to +70°C, 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 = 1kΩ. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER Full-Scale Bandwidth Small Signal Bandwidth SYMBOL f-1.3dB f-1.3dB Differential Input Resistance RIN Input Effective Capacitance CIN CONDITIONS VOUT = 1.5VP-P, 1.3dB bandwidth, gain = 10dB MIN TYP Differential output capacitance is 10pF, capacitance to GND at each single-ended output is 60pF, RL = 1kΩ 18 No capacitive load RL = 1kΩ 29 MAX UNITS MHz VOUT = 1.5mVP-P, 3dB bandwidth, gain = 10dB 30 170 200 230 Ω 15 pF 100 Ω Maximum Gain +29.5 dB Minimum Gain -12.5 dB 42 dB Differential Output Resistance fRF = 10MHz, each input to ground MHz ROUT Gain Range Absolute Gain Error TA = +25°C, full gain range 0% to 100%, VREF = 5V VGA Gain Response Time 40dB gain change to within 1dB final value 1 µs Input-Referred Noise VG_CTL set for maximum gain, no input signal 2 nV/√Hz Output-Referred Noise VG_CTL set for +10dB of gain ±0.25 No input signal 22 VOUT = 1.5VP-P, 1kHz offset 55 VG_CLAMP_MODE = 1, VG_CTL set for +10dB of gain, fRF = 5MHz, VOUT = 1.5VP-P Second Harmonic IMD3 dB nV/√Hz -70 dBc HD2 Third-Order Intermodulation Distortion ±1.5 VG_CLAMP_MODE = 1, VG_CTL set for +10dB of gain, fRF = 10MHz, VOUT = 1.5VP-P -55 -65 VG_CLT set for +10dB of gain, fRF1 = 5MHz, fRF2 = 5.01MHz, VOUT = 1.5VP-P, VREF = 5V (Note 4) -40 -52 dBc _______________________________________________________________________________________ 3 MAX2037 AC ELECTRICAL CHARACTERISTICS AC ELECTRICAL CHARACTERISTICS (continued) (Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, TA = 0°C to +70°C, 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 = 1kΩ. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Channel-to-Channel Crosstalk VOUT = 1VP-P differential, fRF = 10MHz, VG_CTL set for +10dB of gain -80 dB Maximum Output Voltage at Clamp ON VG_CLAMP_MODE = 0, VG_CTL set for +20dB of gain, 350mVP-P differential input 2.4 VP-P differential Maximum Output Voltage at Clamp OFF VG_CLAMP_MODE = 1, VG_CTL set for +20dB of gain, 350mVP-P differential input 2.8 VP-P differential Note 2: Specifications at TA = +25°C and TA = +70°C are guaranteed by production test. Specifications at TA = 0°C 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 = 1kΩ, TA = 0°C to +70°C. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) 4.0 -40 VOUT = 1.5VP-P DIFFERENTIAL VMOD = 50mVP-P, fCARRIER = 5MHz, GAIN = 10dB -50 VOUT = 1VP-P DIFFERENTIAL -10 -20 3.0 2.5 2.0 -60 IMD3 (dBc) PSMR (dBc) 3.5 -70 -30 f = 10MHz -40 -50 -80 1.5 -60 1.0 -90 0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 FREQUENCY (MHz) f = 2MHz -80 -100 0 f = 5MHz -70 0.5 4 0 MAX2037 toc02 VIN1 = 35mVP-P DIFFERENTIAL VIN2 = 87.5mVP-P DIFFERENTIAL GAIN = 20dB 4.5 MAX2037toc01 5.0 TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. GAIN POWER SUPPLY MODULATION RATIO MAX2037toc03 OVERDRIVE PHASE DELAY vs. FREQUENCY OVERDRIVE PHASE DELAY (ns) MAX2037 Ultrasound Variable-Gain Amplifier 0 25 50 75 100 125 150 175 200 FREQUENCY (kHz) -15 -5 5 15 GAIN (dB) _______________________________________________________________________________________ 25 35 Ultrasound Variable-Gain Amplifier SECOND HARMONIC DISTORTION vs. GAIN THIRD HARMONIC DISTORTION vs. GAIN VOUT = 1VP-P DIFFERENTIAL -20 VOUT = 1VP-P DIFFERENTIAL -10 -20 -30 -30 f = 12MHz -40 HD3 (dBc) HD2 (dBc) MAX2037 toc05 0 MAX2037 toc04 0 -10 -50 -60 -70 f = 12MHz -40 f = 5MHz -50 -60 -70 f = 5MHz -80 -80 -90 f = 2MHz -90 f = 2MHz -100 -100 -15 -5 5 15 25 35 -15 GAIN (dB) -5 5 15 25 35 GAIN (dB) OVERLOAD RECOVERY TIME OVERLOAD RECOVERY TIME MAX2037toc07 MAX2037toc06 DIFFERENTIAL OUTPUT 1.0V/div f = 5MHz DIFFERENTIAL OUTPUT 2.0V/div f = 5MHz DIFFERENTIAL INPUT 2.0V/div DIFFERENTIAL INPUT 1.0V/div 400ns/div 400ns/div CHANNEL-TO-CHANNEL CROSSTALK vs. GAIN CHANNEL-TO-CHANNEL CROSSTALK vs. FREQUENCY -65 -30 MAX2037 toc08 -60 VOUT = 1.5VP-P DIFFERENTIAL f = 10MHz, ADJACENT CHANNELS -70 -50 CROSSTALK (dB) CROSSTALK (dB) VOUT = 1VP-P DIFFERENTIAL GAIN = 10dB, ADJACENT CHANNELS -40 MAX2037toc09 OUTPUT 100mVP-P TO OVERLOAD AND BACK TO 100mVP-P OUTPUT 1VP-P TO OVERLOAD AND BACK TO 1VP-P -75 -80 -85 -60 -70 -80 -90 -90 -95 -100 -110 -100 -15 -5 5 15 GAIN (dB) 25 35 1 10 100 FREQUENCY (MHz) _______________________________________________________________________________________ 5 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 = 1kΩ, TA = 0°C to +70°C. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) 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 = 1kΩ, TA = 0°C to +70°C. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) 35 40 f = 5MHz 25 30 20 GAIN (dB) GAIN (dB) 30 5 25 20 15 -5 10 10 -15 5 0 -25 5 15 25 -2.5 -1.5 -0.5 0.5 1.5 0.1 2.5 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY 20 VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +0.6VP-P DIFFERENTIAL 15 10 GAIN (dB) GAIN (dB) -5 10 0 -10 5 -5 -15 0 -10 -20 -5 -15 -25 -10 -30 -20 1 10 100 1000 VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +1.5VP-P 5 5 MAX2037 toc15 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY 15 0.1 1 10 100 0.1 1000 1 10 100 1000 FREQUENCY (MHz) FREQUENCY (MHz) LARGE-SIGNAL BANDWIDTH vs. FREQUENCY LARGE-SIGNAL BANDWIDTH vs. FREQUENCY HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT VOLTAGE -10 -15 GAIN (dB) -10 -20 -20 -25 -25 -30 -30 -35 -35 10 FREQUENCY (MHz) 100 1000 VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 10dB -10 -20 -30 THIRD HARMONIC -40 -50 -60 -70 SECOND HARMONIC -80 -90 -40 1 0 MAX2037 toc18 -5 -5 -15 VOUT = 0.5VP-P DIFFERENTIAL VG_CTL = +2VP-P DIFFERENTIAL HARMONIC DISTORTION (dBc) MAX2037 toc16 0 MAX2037 toc17 FREQUENCY (MHz) VOUT = 1VP-P DIFFERENTIAL VG_CTL = +1.7VP-P DIFFERENTIAL 0.1 1000 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY 0 0 100 FREQUENCY (MHz) 10 5 10 VG_CTL (VP-P DIFFERENTIAL) 20 0.1 1 GAIN (dB) VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = -1VP-P DIFFERENTIAL 25 35 MAX2037 toc14 30 -5 MAX2037 toc13 -15 GAIN (dB) VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = -2VP-P DIFFERENTIAL 35 15 0 6 40 MAX2037toc12 f = 5MHz MAX2037toc11 50 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY GAIN vs. DIFFERENTIAL ANALOG CONTROL VOLTAGE (VG_CTL) MAX2037toc10 OUTPUT-REFERRED NOISE VOLTAGE (nV/√Hz) OUTPUT-REFERRED NOISE VOLTAGE vs. GAIN GAIN (dB) MAX2037 Ultrasound Variable-Gain Amplifier -100 0.1 1 10 FREQUENCY (MHz) 100 1000 0 0.5 1.0 1.5 2.0 2.5 DIFFERENTIAL OUTPUT VOLTAGE (VP-P) _______________________________________________________________________________________ 3.0 Ultrasound Variable-Gain Amplifier THIRD HARMONIC -60 -65 -70 -75 SECOND HARMONIC -80 -85 MAX2037 toc20 VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 10dB -45 -50 -55 THIRD HARMONIC -60 -65 -70 -75 SECOND HARMONIC -80 -85 -90 0 -90 -20 -30 -50 -60 -70 -95 -90 -100 -100 1100 1400 1700 2000 5 25 45 65 85 TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. FREQUENCY VOUT = 1VP-P DIFFERENTIAL GAIN = 10dB 45 20 30 40 50 FREQUENCY (MHz) SAMPLE SIZE = 202 UNITS, fIN_ = 5MHz, GAIN = 10dB 40 -20 35 % OF UNITS IMD3 (dBc) 10 GAIN ERROR HISTOGRAM 50 MAX2037 toc22 0 -10 0 105 DIFFERENTIAL OUTPUT LOAD (pF) MAX2037 toc23 800 DIFFERENTIAL OUTPUT LOAD (Ω) SECOND HARMONIC -80 -100 -30 -40 30 25 20 15 -50 10 -60 5 0 -70 0 5 10 15 20 25 FREQUENCY (MHz) -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) OUTPUT COMMON-MODE OFFSET VOLTAGE vs. GAIN 200 MAX2037 toc24 20 DIFFERENTIAL OUTPUT IMPEDANCE MAGNITUDE vs. FREQUENCY 15 MAX2037 toc25 500 THIRD HARMONIC -40 -95 180 10 160 5 |ZOUT| 200 VOUT = 1VP-P DIFFERENTIAL GAIN = 10dB -10 HARMONIC DISTORTION (dBc) -55 -40 HARMONIC DISTORTION (dBc) -50 VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 10dB OFFSET VOLTAGE (mV) HARMONIC DISTORTION (dBc) -45 MAX2037 toc19 -40 HARMONIC DISTORTION vs. FREQUENCY HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT LOAD CAPACITANCE MAX2037 toc21 HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT LOAD RESISTANCE 0 -5 140 120 100 -10 80 -15 60 -20 -15 -5 5 15 GAIN (dB) 25 35 0.1 1 10 100 FREQUENCY (MHz) _______________________________________________________________________________________ 7 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 = 1kΩ, TA = 0°C to +70°C. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) Ultrasound Variable-Gain Amplifier MAX2037 Pin Description PIN 8 NAME FUNCTION 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 VGIN3- VGA Channel 3 Inverting Differential Input 4 VGIN3+ VGA Channel 3 Noninverting Differential Input 8 VGIN4- VGA Channel 4 Inverting Differential Input 9 VGIN4+ VGA Channel 4 Noninverting Differential Input 13 EXT_C1 External Compensation. Connect a 4.7µF capacitor to ground. 14 EXT_C2 External Compensation. Connect a 4.7µF capacitor to ground. 15 EXT_C3 External Compensation. Connect a 4.7µF capacitor to ground. 16, 39, 42, 46, 54, 72, 82, 87 VCC 17 VGIN5- 18 VGIN5+ VGA Channel 5 Noninverting Differential Input 22 VGIN6- VGA Channel 6 Inverting Differential Input 23 VGIN6+ VGA Channel 6 Noninverting Differential Input 27 VGIN7- VGA Channel 7 Inverting Differential Input 28 VGIN7+ VGA Channel 7 Noninverting Differential Input 32 VGIN8- VGA Channel 8 Inverting Differential Input 33 VGIN8+ VGA Channel 8 Noninverting Differential Input GND Ground 5V Power Supply. Bypass each VCC supply to ground with 0.1µF capacitors as close to the pins as possible. VGA Channel 5 Inverting Differential Input 5V Reference Supply. Bypass to GND with a 0.1µF 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. 37, 93 VREF 38 EXT_RES 40 PD 49 VGOUT8+ VGA Channel 8 Noninverting Differential Output 50 VGOUT8- VGA Channel 8 Inverting Differential Output 52 VGOUT7+ VGA Channel 7 Noninverting Differential Output 53 VGOUT7- VGA Channel 7 Inverting Differential Output 56 VGOUT6+ VGA Channel 6 Noninverting Differential Output 57 VGOUT6- VGA Channel 6 Inverting Differential Output 60 VGOUT5+ VGA Channel 5 Noninverting Differential Output External Resistor. Connect a 7.5kΩ resistor to ground. Power-Down Switch. Drive PD high to set the device in power-down mode. Drive PD low for normal operation. _______________________________________________________________________________________ Ultrasound Variable-Gain Amplifier PIN NAME FUNCTION 61 VGOUT5- VGA Channel 5 Inverting Differential Output 62 VG_CTL- VGA Analog Gain-Control Inverting Input 63 VG_CTL+ VGA Analog Gain-Control Noninverting Input 67 VGOUT4+ VGA Channel 4 Noninverting Differential Output 68 VGOUT4- VGA Channel 4 Inverting Differential Output 70 VGOUT3+ VGA Channel 3 Noninverting Differential Output 71 VGOUT3- VGA Channel 3 Inverting Differential Output 74 VGOUT2+ VGA Channel 2 Noninverting Differential Output 75 VGOUT2- VGA Channel 2 Inverting Differential Output 77 VGOUT1+ VGA Channel 1 Noninverting Differential Output 78 VGOUT1- VGA Channel 1 Inverting Differential Output 86 VG_CLAMP_MODE 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. 94 VGIN1- VGA Channel 1 Inverting Differential Input 95 VGIN1+ VGA Channel 1 Noninverting Differential Input 99 VGIN2- VGA Channel 2 Inverting Differential Input 100 VGIN2+ VGA Channel 2 Noninverting Differential Input — EP Exposed pad. Internally connected to GND. Solder the exposed pad to the ground plane using multiple vias. 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. _______________________________________________________________________________________ 9 MAX2037 Pin Description (continued) MAX2037 Ultrasound Variable-Gain Amplifier Applications Information External Compensation External compensation is required for bypassing internal biasing circuitry. Connect, as close as possible, individual 4.7µF capacitors from each pin EXT_C1, EXT_C2, and EXT_C3 (pin 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 7.5kΩ 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 200Ω. The differential outputs are capable of driving a differential load resistance of 1000Ω. The output impedance is 100Ω 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. 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. -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. 10 f1 - (f2 - f1) f1 f2 f2 + (f2 - f1) Figure 1. Ultrasound IMD3 Measurement Technique ______________________________________________________________________________________ Ultrasound Variable-Gain Amplifier MAX2037 ZIN CONTROL D2, D1, D0 SINGLE CHANNEL MAX2034 SINGLE CHANNEL +V MAX2037 VG_CTL+ VG_CTL18nF 100nF VIN 100nF 100nF 50Ω VGIN_+ VG_OUT_+ VGA VGIN_- TO A SINGLE CHANNEL OF VG_OUT_100nF 50Ω 100nF MAX1436 ADC 100nF -V Figure 2. Typical Per-Channel Ultrasound-Imaging Application 76 77 78 79 GND GND GND VGOUT1VGOUT1+ GND 81 80 GND GND VCC 82 84 83 VG_CLAMP_MODE GND 85 GND VCC 87 88 89 GND GND GND GND 90 91 92 93 94 GND VGIN1+ VGIN1VREF 95 96 97 VGIN2GND GND 100 99 98 VGIN2+ TOP VIEW 86 Pin Configuration + GND 1 75 VGOUT2- GND VGIN3VGIN3+ GND GND GND 2 74 3 73 VGOUT2+ GND 4 72 VCC 5 71 6 70 7 69 VGIN4- 8 68 VGIN4+ GND GND GND 9 67 10 66 11 65 VGOUT3VGOUT3+ GND VGOUT4VGOUT4+ GND GND 64 GND 63 VG_CTL+ 62 VG_CTLVGOUT5- 12 EXT_C1 EXT_C2 EXT_C3 13 15 61 MAX2037 14 VCC 16 60 VGIN5- 17 59 VGIN5+ 18 58 VGOUT5+ GND GND GND GND GND VGIN6- 19 57 VGOUT6- 20 56 VGOUT6+ 21 55 22 54 VGIN6+ 23 53 GND GND 24 52 GND VCC VGOUT7VGOUT7+ 51 GND 50 47 48 GND GND VGOUT8+ VGOUT8- 46 45 44 43 42 41 GND GND GND VCC 40 PD GND VCC 37 38 39 EXT_RES VCC 36 GND GND VREF 32 33 34 35 31 GND VGIN8VGIN8+ GND 30 29 VGIN7+ GND GND 26 27 28 GND VGIN7*EP = EXPOSED PAD 49 *EP 25 TQFP (14mm × 14mm) ______________________________________________________________________________________ 11 MAX2037 Ultrasound Variable-Gain Amplifier Chip Information PROCESS: Silicon Complementary Bipolar 12 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 21-0085 ______________________________________________________________________________________ Ultrasound Variable-Gain Amplifier REVISION NUMBER REVISION DATE 0 10/06 Initial release 1 2/09 Updated various sections DESCRIPTION PAGES CHANGED — 1–7, 9, 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 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX2037 Revision History