General Description
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 dif-
ferential inputs and outputs and a total gain range of
typically 50dB. In addition, the VGAs offer very low out-
put-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-chan-
nel ultrasound beamforming focus error. The device’s
differential outputs are designed to directly drive ultra-
sound ADCs through an external passive anti-aliasing
filter. A switchable clamp is also provided at each ampli-
fier’s outputs to limit the output signals, thereby prevent-
ing 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 avail-
able in a 100-pin TQFP package with an exposed pad.
Electrical performance is guaranteed over a 0°C to
+70°C temperature range.
Applications
Ultrasound Imaging Sonar
Features
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
*
See the Ultrasound-Specific IMD3 Specification in the
Applications Information section.
MAX2035
Ultrasound Variable-Gain Amplifier
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-0630; Rev 1; 2/09
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.
EP = Exposed pad.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
-
Denotes a package containing lead(Pb).
T = Tape and reel.
D = Dry packing.
PART TEMP RANGE PIN-PACKAGE
MAX2035CCQ-D 0°C to +70°C 100 TQFP-EP
MAX2035CCQ-TD 0°C to +70°C 100 TQFP-EP
MAX2035CCQ+D 0°C to +70°C 100 TQFP-EP
MAX2035CCQ+TD 0°C to +70°C 100 TQFP-EP
Functional Diagram
MAX2035
BIAS
CIRCUITRY
GND EXT_RES
VCC VREF
PD
VG_CTL+
VG_CTL- VG_CLAMP_MODE
VGOUT1+
VGOUT1-
VGOUT8+
VGOUT8-
VGIN1+
VGIN1-
VGIN8+
VGIN8-
-10.5dB TO +39.5dB
VGA 50Ω
50Ω
VGA 50Ω
50Ω
MAX2035
Ultrasound Variable-Gain Amplifier
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, 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, TA= 0°C to +70°C. Typical
values are at VCC = VREF = 5V, TA= +25°C, unless otherwise noted.) (Note 2)
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.
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
PARAMETER SYMBOL CONDTIONS MIN TYP MAX UNITS
Supply Voltage Range VCC 4.75 5 5.25 V
VCC External Reference Voltage
Range VREF (Note 3) 4.75 5 5.25 V
PD = 0 204 231
Total Power-Supply Current Refers to VCC supply
current plus VREF current PD = 1 27 33 mA
VCC Supply Current IVCC 192 216 mA
VREF Current IREF 12 15 mA
Current Consumption per
Amplifier Channel Refers to VCC supply current 24 27 mA
Minimum gain +2
Differential Analog Control
Voltage Range Maximum gain -2 VP-P
Differential Analog Control
Common-Mode Voltage VCM 2.85 3.0 3.15 V
Analog Control Input Source/Sink
Current 4.5 5 mA
LOGIC INPUTS
CMOS Input-High Voltage VIH 2.3 V
CMOS Input-Low Voltage VIL 0.8 V
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
MAX2035
Ultrasound Variable-Gain Amplifier
_______________________________________________________________________________________ 3
AC ELECTRICAL CHARACTERISTICS
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, 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, TA= 0°C to +70°C. Typical
values are at VCC = VREF = 5V, TA= +25°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Differential output
capacitance is 10pF,
capacitance to GND at
each single-ended
outp ut i s 60p F, RL = 1kΩ
17
Large-Signal Bandwidth f-3dB
VOUT = 1.5VP-P,
3dB bandwidth,
gain = 20dB
No capacitive load,
RL = 1kΩ22
MHz
Differential Input Resistance RIN 170 200 230 Ω
Input Effective Capacitance CIN fRF = 10MHz, each input to ground 15 pF
Differential Output Resistance ROUT 100 Ω
Maximum Gain 39.5 dB
Minimum Gain -10.5 dB
Gain Range 50 dB
TA = +25°C , -2.0V < V G_CTL < -1.8V , VREF = 5V ±0.6
TA = +25°C, -1.8V < VG_CTL < +1.2V, VRE F = 5V ±0.5
Absolute Gain Error
TA = + 25°C, + 1.2V < V G_CTL < +2.0V, V
REF = 5V ±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
No input signal 60
Output-Referred Noise VG_CTL set for
+20dB of gain VOUT = 1.5VP-P,
1kHz offset 120 nV/Hz
VG_CLAMP_MODE = 1,
VG_CTL set for +20dB of gain,
fRF = 5MHz, VOUT = 1.5VP-P
-55 -62
Second Harmonic HD2 VG_CLAMP_MODE = 1,
VG_CTL set for +20dB of gain,
fRF = 10MHz, VOUT = 1.5VP-P
-62
dBc
Third-Order Intermodulation
Distortion IMD3
VG_CLT set for +20dB of gain,
fRF1 = 5MHz, fRF2 = 5.01MHz,
VOUT = 1.5VP-P, VREF = 5V (Note 4)
-40 -52 dBc
MAX2035
Ultrasound Variable-Gain Amplifier
4 _______________________________________________________________________________________
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 val-
ues are at VCC = VREF = 5V, VCM = 3.0V, TA= +25°C, unless otherwise noted.)
OVERDRIVE PHASE DELAY
vs. FREQUENCY
MAX2035 toc01
VIN1 = 35mVP-P DIFFERENTIAL
VIN2 = 87.5mVP-P DIFFERENTIAL
GAIN = 20dB
5.0
4.5
4.0
3.5
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
OVERDRIVE PHASE DELAY (ns)
FREQUENCY (MHz)
17.5 20.0
POWER-SUPPLY MODULATION RATIO
MAX2035 toc02
VOUT = 1.5VP-P DIFFERENTIAL
VMOD = 50mVP-P, fCARRIER = 5MHz,
GAIN = 20dB
-30
-40
-50
-60
-70
-80
-90
0 25 50 75 100 125 150
PSMR (dBc)
FREQUENCY (kHz)
175 200
TWO-TONE ULTRASOUND-SPECIFIC
IMD3 vs. GAIN
MAX2035 toc03
-30
-40
-50
-60
-70
-80
-20
-10
0
-15-5 5 15253545
IMD3 (dBc)
GAIN (dB)
VOUT = 1VP-P DIFFERENTIAL
GAIN = 20dB
f = 2MHz, 5MHz
f = 10MHz
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
section.
AC ELECTRICAL CHARACTERISTICS (continued)
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = (3/5)VREF, 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, TA= 0°C to +70°C. 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 +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
d i ffer enti al
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
d i ffer enti al
MAX2035
Ultrasound Variable-Gain Amplifier
_______________________________________________________________________________________ 5
OVERLOAD RECOVERY TIME
MAX2035 toc07
OUTPUT OVERLOAD TO 100mVP-P
f = 5MHz DIFFERENTIAL
INPUT
200mV/div
DIFFERENTIAL
OUTPUT
500mV/div
CHANNEL-TO-CHANNEL CROSSTALK
vs. GAIN
MAX2035 toc08
-65
-70
-75
-80
-85
-100
-95
-90
-60
-15 -5 5 15 25 35 45
CROSSTALK (dB)
GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL
f = 10MHz, ADJACENT CHANNELS
-30
-110
1 10 100
CHANNEL-TO-CHANNEL CROSSTALK
vs. FREQUENCY
-90
-100
MAX2035 toc09
FREQUENCY (MHz)
CROSSTALK (dB)
-70
-80
-60
-50
-40
VOUT = 1VP-P DIFFERENTIAL
GAIN = 20dB, ADJACENT CHANNELS
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 val-
ues are at VCC = VREF = 5V, VCM = 3.0V, TA= +25°C, unless otherwise noted.)
SECOND-HARMONIC DISTORTION
vs. GAIN
MAX2035 toc04
-30
-40
-50
-60
-70
-100
-90
-80
-20
-10
0
-15 -5 5 15 25 35 45
HD2 (dBc)
GAIN (dB)
f = 2MHz
VOUT = 1VP-P DIFFERENTIAL
f = 5MHz
f = 12MHz
THIRD-HARMONIC DISTORTION
vs. GAIN
MAX2035 toc05
-30
-40
-50
-60
-70
-100
-90
-80
-20
-10
0
-15 -5 5 15 25 35 45
HD3 (dBc)
GAIN (dB)
VOUT = 1VP-P DIFFERENTIAL
f = 12MHz f = 5MHz
f = 2MHz
OVERLOAD RECOVERY TIME
MAX2035 toc06
OUTPUT OVERLOAD TO 1VP-P
f = 5MHz DIFFERENTIAL
INPUT
200mV/div
DIFFERENTIAL
OUTPUT
500mV/div
MAX2035
Ultrasound Variable-Gain Amplifier
6 _______________________________________________________________________________________
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
MAX2035 toc13
40
35
30
25
20
15
10
5
0
0.1 10 1001 1000
FREQUENCY (MHz)
GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = -0.8VP-P DIFFERENTIAL
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
MAX2035 toc14
30
25
20
15
10
5
0
-5
-10
0.1 10 1001 1000
FREQUENCY (MHz)
GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = +0.2VP-P DIFFERENTIAL
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
MAX2035 toc15
20
15
10
5
0
-5
-10
-15
-20
0.1 10 1001 1000
GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = +1.2VP-P DIFFERENTIAL
FREQUENCY (MHz)
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
MAX2035 toc16
10
5
0
-5
-10
-15
-20
-25
-30
0.1 10 1001 1000
GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = +1.7VP-P DIFFERENTIAL
FREQUENCY (MHz)
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
MAX2035 toc17
0
-5
-10
-15
-20
-25
-30
-35
-40
0.1 10 1001 1000
GAIN (dB)
VOUT = 1VP-P DIFFERENTIAL
VG_CTL = +2VP-P DIFFERENTIAL
FREQUENCY (MHz)
HARMONIC DISTORTION
vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX2035 toc18
-100
-70
-80
-90
-60
-50
-40
-30
-20
-10
0
0 1.00.5 1.5 2.0 2.5 3.0
DIFFERENTIAL OUTPUT VOLTAGE (VP-P)
HARMONIC DISTORTION (dBc)
f = 5MHz, GAIN = 20dB
THIRD HARMONIC
SECOND HARMONIC
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 val-
ues are at VCC = VREF = 5V, VCM = 3.0V, TA= +25°C, unless otherwise noted.)
OUTPUT-REFERRED NOISE VOLTAGE
vs. GAIN
MAX2035 toc10
80
70
60
50
40
30
-15-5 5 15253545
OUTPUT-REFERRED NOISE VOLTAGE (nV/Hz)
GAIN (dB)
f = 5MHz
GAIN vs. DIFFERENTIAL ANALOG
CONTROL VOLTAGE (VG_CTL)
MAX2035 toc11
-15
5
-5
25
15
35
45
-2.5 2.5
VG_CTL (VP-P DIFFERENTIAL)
GAIN (dB)
-0.5-1.5 0.5 1.5
f = 5MHz
50
45
40
35
30
25
20
15
10
0.1 10 1001 1000
FREQUENCY (MHz)
GAIN (dB)
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
MAX2035 toc12
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = -2VP-P DIFFERENTIAL
MAX2035
Ultrasound Variable-Gain Amplifier
_______________________________________________________________________________________ 7
TWO-TONE ULTRASOUND-SPECIFIC IMD3
vs. FREQUENCY
MAX2035 toc22
-70
-20
-30
-40
-50
-60
-10
0
0105152025
FREQUENCY (MHz)
IMD3 (dBc)
VOUT = 1VP-P DIFFERENTIAL
GAIN = 20dB
0
10
5
25
20
15
30
35
45
40
50
-4.50 -3.00
-2.25-3.75
-1.50
-0.75
0.75
1.50
2.25
3.00
3.75
4.50
GAIN ERROR (dB)
% OF UNITS
GAIN ERROR HISTOGRAM
MAX2035 toc23
SAMPLE SIZE = 188 UNITS
fIN_ = 5MHz, GAIN = 20dB
-100
-75
-50
-25
0
25
50
75
100
-15 5-5 15 25 35 45
GAIN (dB)
OFFSET VOLTAGE (mV)
OUTPUT COMMON-MODE OFFSET VOLTAGE
vs. GAIN
MAX2035 toc24
DIFFERENTIAL OUTPUT IMPEDANCE
MAGNITUDE vs. FREQUENCY
MAX2035 toc25
0.1 10 100
FREQUENCY (MHz)
ZOUT (Ω)
1
200
60
80
100
120
140
180
160
HARMONIC DISTORTION
vs. DIFFERENTIAL OUTPUT LOAD RESISTANCE
MAX2035 toc19
-100
-75
-80
-85
-90
-95
-70
-65
-60
-55
-50
-45
-40
200 800500 1100 1400 1700 2000
DIFFERENTIAL OUTPUT LOAD (Ω)
HARMONIC DISTORTION (dBc)
VOUT = 1VP-P DIFFERENTIAL
f = 5MHz, GAIN = 20dB
THIRD HARMONIC
SECOND HARMONIC
HARMONIC DISTORTION
vs. DIFFERENTIAL OUTPUT LOAD CAPACITANCE
MAX2035 toc20
-100
-75
-80
-85
-90
-95
-70
-65
-60
-55
-50
-45
-40
54525 65 85 105
DIFFERENTIAL OUTPUT LOAD (pF)
HARMONIC DISTORTION (dBc)
VOUT = 1VP-P DIFFERENTIAL
f = 5MHz, GAIN = 20dB
THIRD HARMONIC
SECOND HARMONIC
HARMONIC DISTORTION
vs. FREQUENCY
MAX2035 toc21
-100
-50
-60
-70
-80
-90
-40
-30
-20
-10
0
02010 30 40 50
FREQUENCY (MHz)
HARMONIC DISTORTION (dBc)
VOUT = 1VP-P DIFFERENTIAL
GAIN = 20dB
THIRD HARMONIC
SECOND HARMONIC
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 val-
ues are at VCC = VREF = 5V, VCM = 3.0V, TA= +25°C, unless otherwise noted.)
MAX2035
Ultrasound Variable-Gain Amplifier
8 _______________________________________________________________________________________
Pin Description
PIN 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
GND Ground
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 5V Power Supply. Bypass each VCC supply to ground with 0.1µF capacitors as close to the
pins as possible.
17 VGIN5- VGA Channel 5 Inverting Differential Input
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
37, 93 VREF
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.
38 EXT_RES External Resistor. Connect a 7.5kΩ resistor to ground.
40 PD Power-Down Switch. Drive PD high to set the device in power-down mode. Drive PD low for
normal operation.
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
MAX2035
Ultrasound Variable-Gain Amplifier
_______________________________________________________________________________________ 9
Pin Description (continued)
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 V G_C LAMP _M OD E
V GA C l am p M od e E nab l e. D r i ve V G _C LAM P _M OD E l ow to enab l e V GA cl am p i ng . V G A outp ut
w i l l b e cl am p ed at typ i cal l y 2.2V
P - P
d i ffer enti al . D r i ve V G_C LAM P _M O D E hi g h to d i sab l e V G A
cl am p m od e.
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 MAX2035’s VGAs are optimized for high linearity,
high dynamic range, and low output-noise perfor-
mance, making this component ideal for ultrasound-
imaging applications. The VGA paths also exhibit a
channel-to-channel crosstalk of -80dB at 10MHz and an
absolute gain error of less than ±0.5dB for minimal
channel-to-channel focusing error in an ultrasound sys-
tem. Each VGA path includes circuitry for adjusting
analog gain, an output buffer with differential output
ports (VGOUT_+, VGOUT_-) for driving ADCs, and dif-
ferential 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 differen-
tial gain-control input VG_CTL+ and VG_CTL-. Set the
differential gain-control input voltage at -2V for maxi-
mum 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 trans-
mit-related overload.
Applications Information
External Compensation
External compensation is required for bypassing inter-
nal 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 7.5kΩresistor 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 imped-
ance is 100Ωdifferential. The differential outputs have
a common-mode bias of approximately 3V. AC-couple
these differential outputs if the next stage has a differ-
ent common-mode input range.
Ultrasound-Specific IMD3 Specification
Unlike typical communications specs, the two input
tones are not equal in magnitude for the ultrasound-
specific IMD3 two-tone specification. In this measure-
ment, f1represents 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.
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 pad (EP) of the MAX2035’s TQFP-EP
package provides a low thermal-resistance path to the
die. It is important that the PCB on which the MAX2035
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.
MAX2035
Ultrasound Variable-Gain Amplifier
10 ______________________________________________________________________________________
-25dB
ULTRASOUND
IMD3
f1 - (f2 - f1)f
2 + (f2 - f1)f1f2
Figure 1. Ultrasound IMD3 Measurement Technique
MAX2035
Ultrasound Variable-Gain Amplifier
______________________________________________________________________________________ 11
MAX2035
MAX2034
MAX1434 ADC
VG_CTL+
VG_CTL-
VGOUT_+
VGOUT_-
VGIN_+
VGIN_-
SINGLE CHANNEL
SINGLE CHANNEL
VGA
50Ω100nF
ZIN CONTROL
D2, D1, D0
TO A SINGLE
CHANNEL OF
100nF
50Ω
100nF
100nF
100nF
18nF
100nF
VIN
-V
+V
Figure 2. Typical per-Channel Ultrasound-Imaging Application
VGOUT8-
VGOUT8+
GND
VCC
GND
VCC
GND 26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
GND
GND
GND
GND
VCC
EXT_RES
GND
GND
VREF
GND
PD
VGIN8-
GND
VGIN7+
VGIN7-
GND
GND
VGIN8+
VGOUT1-
GND
GND
VCC
GND
GND
VGIN2+
VGOUT1+
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
51
GND
GND
GND
VGIN4+
GND
VGIN3+
VGIN3-
GND
GND
VGOUT2+
GND
VCC
VGOUT3-
VGOUT3+
GND
VGOUT4-
VGOUT4+
GND
GND
GND
VG_CTL+
VG_CTL-
VGOUT5-
GND
GND
VGOUT6-
VGOUT6+
GND
VCC
VGOUT7-
VGOUT7+
GND
*EP = EXPOSED PAD
VGOUT2-
MAX2035
TOP VIEW
GND
VG_CLAMP_MODE
VCC
GND
GND
GND
GND
GND
GND
VREF
VGIN1-
VGIN1+
GND
GND
VGIN2-
GND
EXT_C1
EXT_C2
EXT_C3
VGIN5-
GND
GND
GND
VCC
GND
GND
VGIN6-
GND
GND
VGIN5+
VGIN6+
VGIN4-
VGOUT5+
TQFP
(14mm x 14mm)
+
*EP
Pin Configuration
MAX2035
Ultrasound Variable-Gain Amplifier
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 21-0116
Chip Information
PROCESS: Silicon Complementary Bipolar
MAX2035
Ultrasound Variable-Gain Amplifier
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.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/06 Initial release
1 2/09 Updated various sections 1–7, 9, 12