Maxim MAX2037 Ultrasound variable-gain amplifier Datasheet

19-0586; Rev 0; 10/06
KIT
ATION
EVALU
E
L
B
AVAILA
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 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 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
Hz Ultra-Low Output-Referred Noise at
22nV/√H
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
*See the Ultrasound-Specific IMD3 Specification in the
Applications Information section.
Sonar
Ordering Information
Functional Diagram
VCC
PART
VREF
MAX2037
VG_CTL+
-12.5dB TO +29.5dB
VG_CTL-
TEMP
RANGE
VG_IN1+
VG_OUT1+
PKG
CODE
MAX2037CCQ-D
0°C to +70°C
100 TQFP-EP†
C100E-3
(14mm x 14mm)
MAX2037CCQ-TD
0°C to +70°C
100 TQFP-EP†
C100E-3
(14mm x 14mm)
MAX2037CCQ+D
0°C to +70°C
100 TQFP-EP†
C100E-3
(14mm x 14mm)
MAX2037CCQ+TD 0°C to +70°C
100 TQFP-EP†
C100E-3
(14mm x 14mm)
VG_CLAMP_MODE
50Ω
PIN-PACKAGE
VGA
VG_IN1•
•
•
50Ω
• •
• •
• •
•
•
•
50Ω
VG_IN8+
VG_OUT1•
•
•
VG_OUT8+
VGA
VG_IN8-
50Ω
BIAS
CIRCUITRY
PD
GND
EXT_RES
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
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 ...................................................................................+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, TA = 0°C to +70°C, 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. 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
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
4.75
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 = VREF = 4.75V to 5.25V, VCM = 2.85V to 3.15V, TA = 0°C to +70°C, 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. Typical values are at VCC = VREF = 5V, TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Full-Scale Bandwidth
Small Signal Bandwidth
Differential Input Resistance
Input Effective Capacitance
SYMBOL
f-1.3dB
f-1.3dB
CONDITIONS
VOUT = 1.5VP-P,
1.3dB
bandwidth, gain
= 10dB
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
RIN
CIN
MIN
30
170
fRF = 10MHz, each input to ground
200
MHz
230
15
Ω
pF
100
Ω
Maximum Gain
+29.5
dB
Minimum Gain
-12.5
dB
Differential Output Resistance
ROUT
Gain Range
42
Absolute Gain Error
TA = +25°C, full gain range 0% to 100%
±0.25
dB
±1.0
dB
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
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
-70
dBc
HD2
Third-Order Intermodulation
Distortion
IMD3
nV/√Hz
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 (Note 3)
-40
-52
dB
_______________________________________________________________________________________
3
MAX2037
AC ELECTRICAL CHARACTERISTICS
AC ELECTRICAL CHARACTERISTICS (continued)
(Figure 2, VCC = VREF = 4.75V to 5.25V, VCM = 2.85V to 3.15V, TA = 0°C to +70°C, 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. 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 +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 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 in the Applications Information 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, 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
-100
0
0
2.5
5.0
7.5 10.0 12.5 15.0 17.5 20.0
FREQUENCY (MHz)
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
f = 2MHz
-80
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)
MAX2037toc05
-10
0
MAX2037toc04
0
-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
MAX2037toc08
-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
MAX2037toc10
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, 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.)
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, 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
-30
-20
-10
1
10
100
0.1
1000
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = +1.5VP-P
5
5
MAX2037toc13d
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
15
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
MAX2037toc14
-5
-5
-15
VOUT = 0.5VP-P DIFFERENTIAL
VG_CTL = +2VP-P DIFFERENTIAL
HARMONIC DISTORTION (dBc)
MAX2037toc13e
0
MAX2037toc13f
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
MAX2037toc13c
30
-5
MAX2037toc13b
-15
GAIN (dB)
VOUT = 1.5VP-P DIFFERENTIAL
VG_CTL = -2VP-P DIFFERENTIAL
35
15
0
6
40
MAX2037toc13a
f = 5MHz
MAX2037toc12
50
LARGE-SIGNAL BANDWIDTH
vs. FREQUENCY
GAIN vs. DIFFERENTIAL ANALOG
CONTROL VOLTAGE (VG_CTL)
MAX2037toc11
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
-90
-55
-60
-65
-70
-75
SECOND HARMONIC
-80
-85
-90
-20
-30
-50
-60
-70
-95
-90
-100
-100
800
1100
1400
1700
5
2000
25
DIFFERENTIAL OUTPUT LOAD (Ω)
45
65
85
105
10
VOUT = 1VP-P DIFFERENTIAL
GAIN = 10dB
20
30
40
50
FREQUENCY (MHz)
GAIN ERROR HISTOGRAM
50
MAX2037toc18
0
45
SAMPLE SIZE = 202 UNITS,
fIN_ = 5MHz, GAIN = 10dB
40
-20
35
% OF UNITS
IMD3 (dBc)
0
DIFFERENTIAL OUTPUT LOAD (pF)
TWO-TONE ULTRASOUND-SPECIFIC IMD3
vs. FREQUENCY
-10
SECOND HARMONIC
-80
-95
500
THIRD HARMONIC
-40
-100
-30
-40
30
25
20
15
-50
10
-60
0
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
5
-70
GAIN ERROR (dB)
DIFFERENTIAL OUTPUT IMPEDANCE
MAGNITUDE vs. FREQUENCY
OUTPUT COMMON-MODE OFFSET VOLTAGE
vs. GAIN
15
200
MAX203toc21
20
MAX2037toc20
180
10
160
5
|ZOUT|
200
VOUT = 1VP-P DIFFERENTIAL
GAIN = 10dB
-10
THIRD HARMONIC
MAX2037toc17
-50
0
MAX2037toc16
VOUT = 1VP-P DIFFERENTIAL
f = 5MHz, GAIN = 10dB
-45
MAX2037 toc19
-55
-40
HARMONIC DISTORTION (dBc)
-50
VOUT = 1VP-P DIFFERENTIAL
f = 5MHz, GAIN = 10dB
OFFSET VOLTAGE (mV)
HARMONIC DISTORTION (dBc)
-45
MAX2037toc15
-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
-5
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, 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.)
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-
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
5V Power Supply. Bypass each VCC supply to ground with 0.1µF capacitors as close to the
pins as possible.
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 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
FUNCTION
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+
—
EP
VGA Channel 2 Noninverting Differential Input
Exposed paddle. Solder the exposed paddle 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 paddle (EP) of the MAX2037’s TQFP-EP
package provides a low thermal-resistance path to the
die. It is important that the PC board on which the
MAX2037 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
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
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
GND
VGIN1+
VGIN1VREF
94
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
68
VGOUT4VGOUT4+
GND
GND
VGIN4-
8
VGIN4+
GND
9
67
10
66
GND
11
65
GND
EXT_C1
EXT_C2
EXT_C3
12
15
61
VGOUT5-
VCC
16
60
VGIN5-
17
59
VGIN5+
18
58
VGOUT5+
GND
GND
GND
19
57
GND
GND
VGIN6-
20
56
21
55
22
54
VGIN6+
23
53
GND
GND
24
52
GND
VCC
VGOUT7VGOUT7+
25
51
GND
63
GND
VG_CTL+
62
VG_CTL-
64
13
50
49
47
48
VGOUT6VGOUT6+
GND
GND
VGOUT8+
VGOUT8-
46
45
GND
VCC
44
43
GND
VCC
GND
GND
41
PD
42
40
EXT_RES
VCC
36
GND
GND
VREF
GND
32
33
34
35
31
30
29
VGIN7+
GND
GND
GND
VGIN8VGIN8+
GND
VGIN7-
26
27
28
14
37
38
39
MAX2037
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
MAX2037
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.
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