19-0630; Rev 0; 10/06 Ultrasound Variable-Gain Amplifier Features The MAX2035 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 50dB. In addition, the VGAs offer very low output-referred noise performance suitable for interfacing with 10-bit ADCs. The MAX2035 VGA is optimized for less than ±0.5dB 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 -62dBc 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 MAX2035 operates from a +5.0V power supply, consuming only 127mW/channel. The device is available in a 100-pin TQFP package with an exposed paddle. 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 MAX2036 Ultrasound VGA Plus CW Doppler Beamformer Maximum Gain, Gain Range, and Output-Referred Noise Optimized for Interfacing with 10-Bit ADCs Maximum Gain of 39.5dB Total Gain Range of 50dB 60nV/√Hz Ultra-Low Output-Referred Noise at 5MHz Pin-for-Pin 12-Bit Compatibility Supported By MAX2037/MAX2038 ±0.5dB Absolute Gain Error Switchable Output VGA Clamp Eliminating ADC Overdrive Fully Differential VGA Outputs for Direct ADC Drive Variable Gain Range Achieves 50dB Dynamic Range -62dBc HD2 at VOUT = 1.5VP-P and fIN = 5MHz Two-Tone Ultrasound-Specific* IMD3 of -52dBc at VOUT = 1.5VP-P and fIN = 5MHz 127mW Consumption per Channel Applications Ultrasound Imaging *See the Ultrasound-Specific IMD3 Specification in the Applications Information section. Sonar Ordering Information Functional Diagram VCC PART VREF MAX2035 VG_CTL+ -10.5dB TO +39.5dB VG_CTLVG_IN1+ 50Ω • • • • • • • • • • • • 50Ω VGA VG_IN8- 50Ω BIAS CIRCUITRY PD GND EXT_RES VG_OUT1+ VG_OUT1• • • PIN-PACKAGE PKG CODE MAX2035CCQ-D 0°C to +70°C 100 TQFP-EP† C100E-3 (14mm x 14mm) MAX2035CCQ-TD 0°C to +70°C 100 TQFP-EP† C100E-3 (14mm x 14mm) MAX2035CCQ+D 0°C to +70°C 100 TQFP-EP† C100E-3 (14mm x 14mm) MAX2035CCQ+TD 0°C to +70°C 100 TQFP-EP† C100E-3 (14mm x 14mm) VG_CLAMP_MODE 50Ω VGA VG_IN1- VG_IN8+ TEMP RANGE VG_OUT8+ VG_OUT8- †EP = Exposed paddle. +Denotes lead-free package. T = Tape-and-reel package. D = Dry packing. ________________________________________________________________ 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. 1 MAX2035 General Description MAX2035 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 ...................................................................................+2°C/W θJA .................................................................................+22°C/W Storage Temperature Range .............................-40°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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, GND = 0V, 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, TA = 0°C to +70°C. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) (Note 1) 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 2) 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 0.8 V LOGIC INPUTS CMOS Input-High Voltage VIH CMOS Input-Low Voltage VIL 2 2.0 _______________________________________________________________________________________ V Ultrasound Variable-Gain Amplifier (Figure 2, VCC = 4.75V to 5.25V, VCM = 3/5 VCC, VREF = 5.0V, GND = 0V, 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.) (Note 1) PARAMETER Large-Signal Bandwidth SYMBOL f-3dB Differential Input Resistance RIN Input Effective Capacitance CIN Differential Output Resistance CONDITIONS VOUT = 1.5VP-P, 3dB bandwidth, gain = 20dB MIN TYP Differential output capacitance is 10pF, capacitance to GND 17 No capacitive load, RL = 1kΩ 22 MAX UNITS MHz 170 fRF = 10MHz, each input to ground 200 15 ROUT 230 Ω pF 100 Ω Maximum Gain 39.5 dB Minimum Gain -10.5 dB 50 dB Gain Range Absolute Gain Error TA = +25°C, -2.0V < VG_CTL < -1.8V ±0.6 TA = +25°C, -1.8V < VG_CTL < +1.2V ±0.5 TA = +25°C, +1.2V < VG_CTL < +2.0V ±1.2 dB VGA Gain Response Time 50dB 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 +20dB of gain No input signal 60 VOUT = 1.5VP-P, 1kHz offset 120 VG_CLAMP_MODE = 1, VG_CTL set for +20dB of gain, fRF = 5MHz, VOUT = 1.5VP-P Second Harmonic -55 -62 dBc HD2 VG_CLAMP_MODE = 1, VG_CTL set for +20dB of gain, fRF = 10MHz, VOUT = 1.5VP-P Third-Order Intermodulation Distortion IMD3 nV/√Hz VG_CLT set for +20dB of gain, fRF1 = 5MHz, fRF2 = 5.01MHz, VOUT = 1.5VP-P (Note 3) -62 -40 -52 dB _______________________________________________________________________________________ 3 MAX2035 AC ELECTRICAL CHARACTERISTICS AC ELECTRICAL CHARACTERISTICS (continued) (Figure 2, VCC = 4.75V to 5.25V, VCM = 3/5 VCC, VREF = 5.0V, GND = 0V, 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.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Channel-to-Channel Crosstalk VOUT = 1VP-P differential, fRF = 10MHz, VG_CTL set for +20dB 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 2.2 VP-P differential Maximum Output Voltage at Clamp OFF VG_CLAMP_MODE = 1, VG_CTL set for +20dB of gain, 350mVP-P differential input 3.4 VP-P differential Note 1: 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 2: 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 3: See the Ultrasound-Specific IMD3 Specification section. Typical Operating Characteristics (Figure 2, VCC = VREF = 4.75V to 5.25V, GND = 0V, 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, VCM = 3.0V, TA = +25°C, unless otherwise noted.) 4.0 -30 VOUT = 1.5VP-P DIFFERENTIAL VMOD = 50mVP-P, fCARRIER = 5MHz, GAIN = 20dB -40 VOUT = 1VP-P DIFFERENTIAL GAIN = 20dB -10 -20 3.5 PSMR (dBc) 3.0 2.5 2.0 IMD3 (dBc) -50 -60 -70 1.5 -30 f = 10MHz -40 -50 -60 1.0 -80 0 -90 0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 FREQUENCY (MHz) f = 2MHz, 5MHz -70 0.5 4 0 MAX2035 toc02 VIN1 = 35mVP-P DIFFERENTIAL VIN2 = 87.5mVP-P DIFFERENTIAL GAIN = 20dB 4.5 MAX2035 toc01 5.0 TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. GAIN POWER-SUPPLY MODULATION RATIO MAX2035 toc03 OVERDRIVE PHASE DELAY vs. FREQUENCY OVERDRIVE PHASE DELAY (ns) MAX2035 Ultrasound Variable-Gain Amplifier -80 0 25 50 75 100 125 150 175 200 FREQUENCY (kHz) -15 -5 5 15 GAIN (dB) _______________________________________________________________________________________ 25 35 45 Ultrasound Variable-Gain Amplifier SECOND-HARMONIC DISTORTION vs. GAIN THIRD-HARMONIC DISTORTION vs. GAIN VOUT = 1VP-P DIFFERENTIAL -20 -20 -30 f = 12MHz -40 -50 HD3 (dBc) f = 5MHz -60 -70 f = 12MHz -40 f = 5MHz -50 -60 -70 -80 -90 -90 -100 -100 -15 -5 f = 2MHz -80 f = 2MHz 5 15 25 35 45 -15 GAIN (dB) -5 5 15 25 45 OVERLOAD RECOVERY TIME OVERLOAD RECOVERY TIME MAX2035 toc07 MAX2035 toc06 f = 5MHz DIFFERENTIAL INPUT 200mV/div f = 5MHz DIFFERENTIAL INPUT 200mV/div DIFFERENTIAL OUTPUT 500mV/div DIFFERENTIAL OUTPUT 500mV/div OUTPUT OVERLOAD TO 100mVP-P OUTPUT OVERLOAD TO 1VP-P CHANNEL-TO-CHANNEL CROSSTALK vs. FREQUENCY CHANNEL-TO-CHANNEL CROSSTALK vs. GAIN -30 MAX2035 toc08 -60 VOUT = 1.5VP-P DIFFERENTIAL f = 10MHz, ADJACENT CHANNELS -65 35 GAIN (dB) VOUT = 1VP-P DIFFERENTIAL GAIN = 20dB, ADJACENT CHANNELS -40 MAX2035 toc09 HD2 (dBc) VOUT = 1VP-P DIFFERENTIAL -10 -30 -50 CROSSTALK (dB) -70 CROSSTALK (dB) MAX2035 toc05 0 MAX2035 toc04 0 -10 -75 -80 -85 -60 -70 -80 -90 -90 -95 -100 -110 -100 -15 -5 5 15 GAIN (dB) 25 35 45 1 10 100 FREQUENCY (MHz) _______________________________________________________________________________________ 5 MAX2035 Typical Operating Characteristics (continued) (Figure 2, VCC = VREF = 4.75V to 5.25V, GND = 0V, 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, VCM = 3.0V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (Figure 2, VCC = VREF = 4.75V to 5.25V, GND = 0V, 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, VCM = 3.0V, TA = +25°C, unless otherwise noted.) f = 5MHz 70 f = 5MHz 35 40 50 GAIN (dB) GAIN (dB) 60 15 35 30 25 5 20 -5 15 10 -15 -5 5 15 25 35 45 -2.5 -1.5 -0.5 0.5 1.5 0.1 2.5 1000 GAIN (dB) LARGE-SIGNAL BANDWIDTH vs. FREQUENCY LARGE-SIGNAL BANDWIDTH vs. FREQUENCY VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +0.2VP-P DIFFERENTIAL 25 20 MAX2035 toc14 30 10 25 15 5 GAIN (dB) 20 GAIN (dB) 30 20 10 0 15 5 -5 10 0 -10 5 -5 -15 0 -10 100 1000 -20 0.1 1 10 100 FREQUENCY (MHz) FREQUENCY (MHz) LARGE-SIGNAL BANDWIDTH vs. FREQUENCY LARGE-SIGNAL BANDWIDTH vs. FREQUENCY VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +1.7VP-P DIFFERENTIAL 0 MAX2035 toc16 10 -5 -10 -5 -15 GAIN (dB) 0 -10 -25 -20 -30 -25 -35 -30 -40 10 100 FREQUENCY (MHz) 1000 0.1 1 10 100 FREQUENCY (MHz) 1000 HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT VOLTAGE -20 -15 1 VOUT = 1VP-P DIFFERENTIAL VG_CTL = +2VP-P DIFFERENTIAL 1000 0 f = 5MHz, GAIN = 20dB -10 HARMONIC DISTORTION (dBc) 10 MAX2035 toc17 1 VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = +1.2VP-P DIFFERENTIAL 15 MAX2035 toc18 MAX2035 toc13 35 0.1 100 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = -0.8VP-P DIFFERENTIAL 5 10 FREQUENCY (MHz) 40 0.1 1 VG_CTL (VP-P DIFFERENTIAL) MAX2035 toc15 40 -15 GAIN (dB) VOUT = 1.5VP-P DIFFERENTIAL VG_CTL = -2VP-P DIFFERENTIAL 45 25 30 6 50 MAX2035 toc11 45 MAX2035 toc10 OUTPUT-REFERRED NOISE VOLTAGE (nV/√Hz) 80 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY GAIN vs. DIFFERENTIAL ANALOG CONTROL VOLTAGE (VG_CTL) MAX2035 toc12 OUTPUT-REFERRED NOISE VOLTAGE vs. GAIN GAIN (dB) MAX2035 Ultrasound Variable-Gain Amplifier -20 -30 THIRD HARMONIC -40 -50 -60 SECOND HARMONIC -70 -80 -90 -100 0.1 1 10 100 FREQUENCY (MHz) 1000 0 0.5 1.0 1.5 2.0 2.5 DIFFERENTIAL OUTPUT VOLTAGE (VP-P) _______________________________________________________________________________________ 3.0 Ultrasound Variable-Gain Amplifier -55 THIRD HARMONIC -65 -70 SECOND HARMONIC -75 -80 -85 -55 -60 THIRD HARMONIC -65 -70 -75 SECOND HARMONIC -80 -85 -90 -90 -95 -95 500 800 1100 1400 1700 25 45 65 85 -40 -50 -60 SECOND HARMONIC -70 -80 0 105 10 VOUT = 1VP-P DIFFERENTIAL GAIN = 20dB 30 40 50 GAIN ERROR HISTOGRAM 50 MAX2035 toc22 0 20 FREQUENCY (MHz) DIFFERENTIAL OUTPUT LOAD (pF) TWO-TONE ULTRASOUND-SPECIFIC IMD3 vs. FREQUENCY -10 THIRD HARMONIC -30 -100 5 2000 DIFFERENTIAL OUTPUT LOAD (Ω) SAMPLE SIZE = 188 UNITS fIN_ = 5MHz, GAIN = 20dB 45 40 -20 35 % OF UNITS IMD3 (dBc) -30 -40 30 25 20 15 -50 10 -60 5 0 -70 FREQUENCY (MHz) -4.50 -3.00 -1.50 0.75 2.25 3.75 -3.75 -2.25 -0.75 1.50 3.00 4.50 GAIN ERROR (dB) OUTPUT COMMON-MODE OFFSET VOLTAGE vs. GAIN DIFFERENTIAL OUTPUT IMPEDANCE MAGNITUDE vs. FREQUENCY 5 10 15 20 100 25 200 75 MAX2035 toc25 0 MAX2035 toc24 180 50 160 25 ZOUT (Ω) 200 -20 -90 -100 -100 VOUT = 1VP-P DIFFERENTIAL GAIN = 20dB MAX2035 toc21 MAX2035 toc20 -50 0 -10 MAX2035 toc23 -60 OFFSET VOLTAGE (mV) HARMONIC DISTORTION (dBc) -50 VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 20dB -45 HARMONIC DISTORTION (dBc) VOUT = 1VP-P DIFFERENTIAL f = 5MHz, GAIN = 20dB -45 -40 MAX2035 toc19 -40 HARMONIC DISTORTION vs. FREQUENCY HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT LOAD CAPACITANCE HARMONIC DISTORTION (dBc) HARMONIC DISTORTION vs. DIFFERENTIAL OUTPUT LOAD RESISTANCE 0 140 120 -25 100 -50 80 -75 60 -100 -15 -5 5 15 GAIN (dB) 25 35 45 0.1 1 10 100 FREQUENCY (MHz) _______________________________________________________________________________________ 7 MAX2035 Typical Operating Characteristics (continued) (Figure 2, VCC = VREF = 4.75V to 5.25V, GND = 0V, 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, VCM = 3.0V, TA = +25°C, unless otherwise noted.) Ultrasound Variable-Gain Amplifier MAX2035 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 GND Ground 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 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 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 FUNCTION VGA Clamp Mode Enable. Drive VG_CLAMP_MODE low to enable VGA clamping. VGA output VG_CLAMP_MODE will be clamped at typically 2.2VP-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 Paddle. Solder the exposed paddle to the ground plane using multiple vias. Detailed Description The MAX2035’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 -10.5dB to +39.5dB, achieving a total dynamic range of typically 50dB. 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 2.2VP-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 MAX2035 Pin Description (continued) MAX2035 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 MAX2035 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 MAX1434 octal ADC). The differential input impedance of the MAX2035 is typically 200Ω. The differential outputs are capable of driving a differential load resistance of 1kΩ. The output impedance is 100Ω differential. The differential outputs have a common-mode bias of approximately 3V. AC-couple these differential outputs if the next stage has a different common-mode input range. PCB Layout The pin configuration of the MAX2035 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 MAX2035’s TQFP-EP package provides a low thermal-resistance path to the die. It is important that the PC board (PCB) on which the MAX2035 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 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 MAX2035 ZIN CONTROL D2, D1, D0 SINGLE CHANNEL MAX2034 SINGLE CHANNEL +V MAX2035 VG_CTL+ VG_CTL18nF 100nF VIN 100nF 100nF 50Ω VGIN_+ VG_OUT_+ VGA VGIN_- TO A SINGLE CHANNEL OF VG_OUT_100nF 50Ω 100nF MAX1434 ADC 100nF -V Figure 2. Typical per-Channel Ultrasound-Imaging Application 76 77 78 79 GND GND GND VGOUT1VGOUT1+ GND 80 81 82 84 83 VG_CLAMP_MODE GND GND GND VCC 85 GND VCC 88 87 GND GND 90 89 GND GND 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 VGOUT3VGOUT3+ GND VGIN4- 8 68 VGIN4+ GND 9 67 10 66 GND GND 11 65 EXT_C1 EXT_C2 EXT_C3 13 15 61 VGOUT5- VCC 16 60 VGIN5VGIN5+ GND GND 17 59 18 58 VGOUT5+ GND GND 19 57 20 56 GND VGIN6- 21 55 22 54 VGIN6+ 23 53 GND GND 24 52 VCC VGOUT7VGOUT7+ 25 51 GND 12 63 GND VG_CTL+ 62 VG_CTL- 64 50 49 47 48 VGOUT6VGOUT6+ GND GND VGOUT8+ VGOUT8- GND 46 45 GND VCC 44 43 GND GND 41 42 40 PD GND VCC EXT_RES VCC 36 GND GND VREF 32 33 34 35 GND 31 30 29 VGIN7+ GND GND GND VGIN8VGIN8+ GND VGIN7- 26 27 28 14 37 38 39 MAX2035 VGOUT4VGOUT4+ GND GND TQFP ______________________________________________________________________________________ 11 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.) 100L,TQFP.EPS MAX2035 Ultrasound Variable-Gain Amplifier PACKAGE OUTLINE 100L TQFP, 14x14x1.0mm 21-0085 B 1 2 PACKAGE OUTLINE, 100L TQFP, 14x14x1.0mm 21-0085 B 2 2 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.