MAX2037 Ultrasound Variable-Gain Amplifier General Description Features

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
PART
VREF
MAX2037
VG_CTL+
-12.5dB TO +29.5dB
VG_CTL-
VG_CLAMP_MODE
50Ω
VGIN1+
VGOUT1+
VGA
VGIN1•
•
•
50Ω
• •
• •
• •
•
•
•
50Ω
VGIN8+
VGOUT1•
•
•
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.
VGOUT8+
VGA
VGIN8-
50Ω
VGOUT8-
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.
www.BDTIC.com/maxim
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
_______________________________________________________________________________________
www.BDTIC.com/maxim
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,
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
±1.5
IMD3
nV/√Hz
-70
HD2
Third-Order Intermodulation
Distortion
dB
dBc
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
_______________________________________________________________________________________
www.BDTIC.com/maxim
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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
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
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
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.
57
VGOUT6-
VGA Channel 6 Inverting Differential Output
60
VGOUT5+
VGA Channel 5 Noninverting Differential Output
_______________________________________________________________________________________
www.BDTIC.com/maxim
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.
_______________________________________________________________________________________
www.BDTIC.com/maxim
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
______________________________________________________________________________________
www.BDTIC.com/maxim
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_+
VGOUT_+
VGA
VGIN_-
TO A SINGLE
CHANNEL OF
VGOUT_100nF
50Ω
100nF
MAX1436 ADC
100nF
-V
Figure 2. Typical Per-Channel Ultrasound-Imaging Application
VGOUT1+
GND
77
76
VGOUT178
79
GND
GND
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
5
71
6
70
7
69
VGIN4-
8
68
VGIN4+
GND
GND
GND
9
67
10
66
11
65
VCC
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
VGIN5VGIN5+
17
59
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
30
29
VGIN7+
GND
GND
GND
VGIN8VGIN8+
GND
26
27
28
GND
VGIN7*EP = EXPOSED PAD
49
*EP
25
TQFP
(14mm × 14mm)
______________________________________________________________________________________
www.BDTIC.com/maxim
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
21-0116
______________________________________________________________________________________
www.BDTIC.com/maxim
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.
www.BDTIC.com/maxim
MAX2037
Revision History