Download MAX2035 Ultrasound Variable-Gain Amplifier General Description Features

19-0630; Rev 1; 2/09
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 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 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
Sonar
*See the Ultrasound-Specific IMD3 Specification in the
Applications Information section.
Ordering Information
Functional Diagram
VCC
PART
VREF
MAX2035CCQ-D
MAX2035
VG_CTL+
-10.5dB TO +39.5dB
VG_CTLVGIN1+
VG_CLAMP_MODE
50Ω
VGA
VGIN1-
50Ω
•
•
•
VGIN8+
• •
• •
• •
•
•
•
50Ω
VGA
VGIN8-
50Ω
VGOUT1+
VGOUT1•
•
•
VGOUT8+
TEMP RANGE
0°C to +70°C
MAX2035CCQ-TD
0°C to +70°C
MAX2035CCQ+D
0°C to +70°C
MAX2035CCQ+TD
0°C to +70°C
PIN-PACKAGE
100 TQFP-EP†
100 TQFP-EP†
100 TQFP-EP†
100 TQFP-EP†
†EP = Exposed pad.
+Denotes a lead(Pb)-free/RoHS-compliant package.
-Denotes a package containing lead(Pb).
T = Tape and reel.
D = Dry packing.
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
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 (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, 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
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 3)
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
2.3
V
_______________________________________________________________________________________
www.BDTIC.com/maxim
Ultrasound Variable-Gain Amplifier
(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
Large-Signal Bandwidth
SYMBOL
f-3dB
Differential Input Resistance
RIN
Input Effective Capacitance
CIN
CONDITIONS
VOUT = 1.5VP-P,
3dB bandwidth,
gain = 20dB
MIN
TYP
Differential output
capacitance is 10pF,
capacitance to GND at
each single-ended
output is 60pF, RL = 1kΩ
17
No capacitive load,
RL = 1kΩ
22
MAX
UNITS
MHz
170
200
230
Ω
15
pF
100
Ω
Maximum Gain
39.5
dB
Minimum Gain
-10.5
dB
50
dB
Differential Output Resistance
fRF = 10MHz, each input to ground
ROUT
Gain Range
TA = +25°C, -2.0V < VG_CTL < -1.8V, VREF = 5V
Absolute Gain Error
±0.6
dB
TA = +25°C, -1.8V < VG_CTL < +1.2V, VREF = 5V
±0.5
TA = +25°C, +1.2V < VG_CTL < +2.0V, VREF = 5V
±1.2
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
Second Harmonic
HD2
Third-Order Intermodulation
Distortion
IMD3
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
-55
-62
dBc
VG_CLAMP_MODE = 1,
VG_CTL set for +20dB of gain,
fRF = 10MHz, VOUT = 1.5VP-P
VG_CLT set for +20dB of gain,
fRF1 = 5MHz, fRF2 = 5.01MHz,
VOUT = 1.5VP-P, VREF = 5V (Note 4)
nV/√Hz
-62
-40
-52
dBc
_______________________________________________________________________________________
www.BDTIC.com/maxim
3
MAX2035
AC ELECTRICAL CHARACTERISTICS
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
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 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.
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, 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
25
GAIN (dB)
_______________________________________________________________________________________
www.BDTIC.com/maxim
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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
5
MAX2035
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, VCM = 3.0V, 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, 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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
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)
_______________________________________________________________________________________
www.BDTIC.com/maxim
7
MAX2035
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, VCM = 3.0V, TA = +25°C, unless otherwise noted.)
MAX2035
Ultrasound Variable-Gain Amplifier
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
3
VGIN3-
VGA Channel 3 Inverting Differential Input
4
VGIN3+
VGA Channel 3 Noninverting Differential Input
8
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
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.
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.
_______________________________________________________________________________________
www.BDTIC.com/maxim
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+
—
EP
VGA Channel 2 Noninverting Differential Input
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 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 ±0.5dB 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.
_______________________________________________________________________________________
www.BDTIC.com/maxim
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 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.
-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
MAX2035
ZIN CONTROL
D2, D1, D0
SINGLE CHANNEL
MAX2034
SINGLE CHANNEL
+V
MAX2035
VG_CTL+
VG_CTL18nF
100nF
VIN
100nF
100nF
50Ω
VGIN_+
VGOUT_+
VGA
VGIN_-
TO A SINGLE
CHANNEL OF
VGOUT_100nF
50Ω
100nF
MAX1434 ADC
100nF
-V
Figure 2. Typical per-Channel Ultrasound-Imaging Application
VGOUT1+
GND
77
76
78
79
GND
GND
GND
VGOUT180
81
82
GND
GND
VCC
84
83
VG_CLAMP_MODE
GND
85
GND
VCC
88
87
GND
GND
90
89
GND
GND
91
92
93
GND
VGIN1+
VGIN1VREF
94
95
96
+
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
EXT_C1
EXT_C2
EXT_C3
9
67
10
66
11
65
12
64
13
63
MAX2035
14
62
15
61
VCC
16
60
VGIN5VGIN5+
GND
GND
GND
VGIN6-
17
59
18
58
19
57
20
56
21
55
22
54
VGIN6+
23
53
GND
GND
24
46
47
48
49
GND
GND
VGOUT8+
VGOUT8-
45
44
43
42
GND
GND
GND
VCC
41
40
PD
GND
VCC
EXT_RES
VCC
37
38
39
36
GND
GND
VREF
32
33
34
35
31
30
29
VGIN7+
GND
GND
GND
VGIN8VGIN8+
GND
26
27
28
VCC
VGOUT3VGOUT3+
GND
VGOUT4VGOUT4+
GND
GND
GND
VG_CTL+
VG_CTLVGOUT5VGOUT5+
GND
GND
VGOUT6VGOUT6+
52
GND
VCC
VGOUT7VGOUT7+
51
GND
50
*EP
25
GND
VGIN7*EP = EXPOSED PAD
97
VGIN2GND
GND
100
99
98
VGIN2+
TOP VIEW
86
Pin Configuration
TQFP
(14mm x 14mm)
______________________________________________________________________________________
www.BDTIC.com/maxim
11
MAX2035
Ultrasound Variable-Gain Amplifier
Package Information
Chip Information
PROCESS: Silicon Complementary Bipolar
12
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
MAX2035
Revision History