19-0630; Rev 1; 2/09
Ultrasound Variable-Gain Amplifier
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 V
OUT
= 1.5V
P-P
and f
IN
=
5MHz, and an ultrasound-specific* two-tone third-order
intermodulation distortion specification of -52dBc at
V
OUT
= 1.5V
P-P
and f
IN
= 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.
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 V
OUT
= 1.5V
P-P
and f
IN
= 5MHz
♦
Two-Tone Ultrasound-Specific* IMD3 of -52dBc at
V
OUT
= 1.5V
P-P
and f
IN
= 5MHz
♦
127mW Consumption per Channel
*See
the Ultrasound-Specific IMD3 Specification in the
Applications Information section.
MAX2035
Applications
Ultrasound Imaging
Sonar
Functional Diagram
V
CC
V
REF
Ordering Information
PART
MAX2035CCQ-D
MAX2035CCQ-TD
MAX2035CCQ+D
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
100 TQFP-EP
†
100 TQFP-EP
†
100 TQFP-EP
†
100 TQFP-EP
†
MAX2035
VG_CTL+
VG_CTL-
VG_IN1+
VG_IN1-
•
•
•
• •
• •
• •
-10.5dB TO +39.5dB
VG_CLAMP_MODE
VGA
50Ω
VG_OUT1+
VG_OUT1-
•
•
•
MAX2035CCQ+TD
†
EP = Exposed pad.
50Ω
•
•
•
VG_IN8+
VG_IN8-
VGA
50Ω
VG_OUT8+
VG_OUT8-
+Denotes
a lead(Pb)-free/RoHs-compliant package.
-Denotes a package containing lead(Pb).
T = Tape and reel.
D = Dry packing.
50Ω
BIAS
CIRCUITRY
PD
GND
EXT_RES
________________________________________________________________
Maxim Integrated Products
1
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.
Ultrasound Variable-Gain Amplifier
MAX2035
ABSOLUTE MAXIMUM RATINGS
V
CC
, V
REF
to GND .................................................-0.3V to +5.5V
Any Other Pins to GND...............................-0.3V to (V
CC
+ 0.3V)
VGA Differential Input Voltage (VGIN_+ - VGIN_-)...........8.0V
P-P
Analog Gain-Control Input Differential Voltage
(VG_CTL+ - VG_CTL-)...................................................8.0V
P-P
Continuous Power Dissipation (T
A
= +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
θ
JC
(Note 1) .....................................................................+2°C/W
θ
JA
(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 four-
layer 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, V
CC
= V
REF
= 4.75V to 5.25V, V
CM
= (3/5)V
REF
, V
GND
= 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, R
L
= 1kΩ, T
A
= 0°C to +70°C. Typical
values are at V
CC
= V
REF
= 5V, T
A
= +25°C, unless otherwise noted.) (Note 2)
PARAMETER
Supply Voltage Range
V
CC
External Reference Voltage
Range
Total Power-Supply Current
V
CC
Supply Current
V
REF
Current
Current Consumption per
Amplifier Channel
Differential Analog Control
Voltage Range
Differential Analog Control
Common-Mode Voltage
Analog Control Input Source/Sink
Current
LOGIC INPUTS
CMOS Input-High Voltage
CMOS Input-Low Voltage
V
IH
V
IL
2.3
0.8
V
V
V
CM
I
VCC
I
REF
Refers to V
CC
supply current
Minimum gain
Maximum gain
2.85
SYMBOL
V
CC
V
REF
(Note 3)
Refers to V
CC
supply
current plus V
REF
current
PD = 0
PD =1
CONDTIONS
MIN
4.75
4.75
TYP
5
5
204
27
192
12
24
+2
-2
3.0
4.5
3.15
5
MAX
5.25
5.25
231
33
216
15
27
UNITS
V
V
mA
mA
mA
mA
V
P-P
V
mA
2
_______________________________________________________________________________________
Ultrasound Variable-Gain Amplifier
AC ELECTRICAL CHARACTERISTICS
(Figure 2, V
CC
= V
REF
= 4.75V to 5.25V, V
CM
= (3/5)V
REF
, V
GND
= 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, R
L
= 1kΩ, T
A
= 0°C to +70°C. Typical
values are at V
CC
= V
REF
= 5V, T
A
= +25°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
Differential output
capacitance is 10pF,
capacitance to GND at
each single-ended
output is 60pF, R
L
= 1kΩ
No capacitive load,
R
L
= 1kΩ
Differential Input Resistance
Input Effective Capacitance
Differential Output Resistance
Maximum Gain
Minimum Gain
Gain Range
T
A
= +25°C, -2.0V < VG_CTL < -1.8V, V
REF
= 5V
Absolute Gain Error
VGA Gain Response Time
Input-Referred Noise
T
A
= +25°C, -1.8V < VG_CTL < +1.2V, V
REF
= 5V
T
A
= +25°C, +1.2V < VG_CTL < +2.0V, V
REF
= 5V
50dB gain change to within 1dB final value
VG_CTL set for maximum gain,
no input signal
VG_CTL set for
+20dB of gain
No input signal
V
OUT
= 1.5V
P-P
,
1kHz offset
-55
R
IN
C
IN
R
OUT
f
RF
= 10MHz, each input to ground
170
MIN
TYP
MAX
UNITS
MAX2035
Large-Signal Bandwidth
f
-3dB
V
OUT
= 1.5V
P-P
,
3dB bandwidth,
gain = 20dB
17
MHz
22
200
15
100
39.5
-10.5
50
±0.6
±0.5
±1.2
1
2
60
120
nV/√Hz
µs
nV/√Hz
dB
230
Ω
pF
Ω
dB
dB
dB
Output-Referred Noise
Second Harmonic
HD2
VG_CLAMP_MODE = 1,
VG_CTL set for +20dB of gain,
f
RF
= 5MHz, V
OUT
= 1.5V
P-P
VG_CLAMP_MODE = 1,
VG_CTL set for +20dB of gain,
f
RF
= 10MHz, V
OUT
= 1.5V
P-P
VG_CLT set for +20dB of gain,
f
RF1
= 5MHz, f
RF2
= 5.01MHz,
V
OUT
= 1.5V
P-P
, V
REF
= 5V (Note 4)
-62
dBc
-62
Third-Order Intermodulation
Distortion
IMD3
-40
-52
dBc
_______________________________________________________________________________________
3
Ultrasound Variable-Gain Amplifier
MAX2035
AC ELECTRICAL CHARACTERISTICS (continued)
(Figure 2, V
CC
= V
REF
= 4.75V to 5.25V, V
CM
= (3/5)V
REF
, V
GND
= 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, R
L
= 1kΩ, T
A
= 0°C to +70°C. Typical
values are at V
CC
= V
REF
= 5V, T
A
= +25°C, unless otherwise noted.) (Note 2)
PARAMETER
Channel-to-Channel Crosstalk
Maximum Output Voltage at
Clamp ON
Maximum Output Voltage at
Clamp OFF
SYMBOL
CONDITIONS
V
OUT
= 1V
P-P
differential, f
RF
= 10MHz,
VG_CTL set for +20dB of gain
VG_CLAMP_MODE = 0,
VG_CTL set for +20dB of gain,
350mV
P-P
differential input
VG_CLAMP_MODE = 1,
VG_CTL set for +20dB of gain,
350mV
P-P
differential input
MIN
TYP
-80
MAX
UNITS
dB
V
P-P
differential
V
P-P
differential
2.2
3.4
Note 2:
Specifications at T
A
= +25°C and T
A
= +70°C are guaranteed by production test. Specifications at T
A
= 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 V
REF
. Use a low-noise supply for
V
REF
. V
CC
and V
REF
can be connected together to share the same supply voltage if the supply for V
CC
exhibits low noise.
Note 4:
See the
Ultrasound-Specific IMD3 Specification
section.
Typical Operating Characteristics
(Figure 2, V
CC
= V
REF
= 4.75V to 5.25V, V
GND
= 0, PD = 0, VG_CLAMP_MODE = 1, f
RF
= 5MHz, capacitance to GND at each of the
VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, R
L
= 1kΩ, T
A
= 0°C to +70°C. Typical val-
ues are at V
CC
= V
REF
= 5V, V
CM
= 3.0V, T
A
= +25°C, unless otherwise noted.)
OVERDRIVE PHASE DELAY
vs. FREQUENCY
MAX2035 toc01
POWER-SUPPLY MODULATION RATIO
MAX2035 toc02
TWO-TONE ULTRASOUND-SPECIFIC
IMD3 vs. GAIN
-10
-20
V
OUT
= 1V
P-P
DIFFERENTIAL
GAIN = 20dB
MAX2035 toc03
5.0
4.5
OVERDRIVE PHASE DELAY (ns)
-30
-40
-50
V
OUT
= 1.5V
P-P
DIFFERENTIAL
V
MOD
= 50mV
P-P
, f
CARRIER
= 5MHz,
GAIN = 20dB
0
4.0
3.5
V
IN1
= 35mV
P-P
DIFFERENTIAL
V
IN2
= 87.5mV
P-P
DIFFERENTIAL
GAIN = 20dB
PSMR (dBc)
IMD3 (dBc)
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 17.5 20.0
FREQUENCY (MHz)
-30
f
= 10MHz
-40
-50
-60
-60
-70
-80
-90
0
25
50
75
100 125 150 175 200
FREQUENCY (kHz)
-70
-80
-15
-5
f
= 2MHz, 5MHz
5
15
GAIN (dB)
25
35
45
4
_______________________________________________________________________________________
Ultrasound Variable-Gain Amplifier
Typical Operating Characteristics (continued)
(Figure 2, V
CC
= V
REF
= 4.75V to 5.25V, V
GND
= 0, PD = 0, VG_CLAMP_MODE = 1, f
RF
= 5MHz, capacitance to GND at each of the
VGA differential outputs is 60pF, differential capacitance across the VGA outputs is 10pF, R
L
= 1kΩ, T
A
= 0°C to +70°C. Typical val-
ues are at V
CC
= V
REF
= 5V, V
CM
= 3.0V, T
A
= +25°C, unless otherwise noted.)
SECOND-HARMONIC DISTORTION
vs. GAIN
MAX2035 toc04
MAX2035
THIRD-HARMONIC DISTORTION
vs. GAIN
-10
-20
-30
HD3 (dBc)
f
= 12MHz
V
OUT
= 1V
P-P
DIFFERENTIAL
MAX2035 toc05
0
-10
-20
-30
HD2 (dBc)
-40
-50
-60
-70
-80
-90
-100
-15
-5
5
15
GAIN (dB)
25
35
f
= 2MHz
f
= 12MHz
f
= 5MHz
V
OUT
= 1V
P-P
DIFFERENTIAL
0
-40
-50
-60
-70
-80
-90
f
= 5MHz
f
= 2MHz
45
-100
-15
-5
5
15
GAIN (dB)
25
35
45
OVERLOAD RECOVERY TIME
MAX2035 toc06
OVERLOAD RECOVERY TIME
MAX2035 toc07
f = 5MHz
DIFFERENTIAL
INPUT
200mV/div
f = 5MHz
DIFFERENTIAL
INPUT
200mV/div
DIFFERENTIAL
OUTPUT
500mV/div
DIFFERENTIAL
OUTPUT
500mV/div
OUTPUT OVERLOAD TO 1V
P-P
OUTPUT OVERLOAD TO 100mV
P-P
CHANNEL-TO-CHANNEL CROSSTALK
vs. GAIN
MAX2035 toc08
CHANNEL-TO-CHANNEL CROSSTALK
vs. FREQUENCY
-40
-50
CROSSTALK (dB)
-60
-70
-80
-90
-100
-110
V
OUT
= 1V
P-P
DIFFERENTIAL
GAIN = 20dB,
ADJACENT CHANNELS
MAX2035 toc09
-60
-65
-70
CROSSTALK (dB)
-75
-80
-85
-90
-95
-100
-15
-5
5
15
GAIN (dB)
25
35
V
OUT
= 1.5V
P-P
DIFFERENTIAL
f
= 10MHz, ADJACENT CHANNELS
-30
45
1
10
FREQUENCY (MHz)
100
_______________________________________________________________________________________
5
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