General Description
The MAX44206 is a low-noise, low-distortion fully differ-
ential operational amplifier suitable for driving high-speed,
high-resolution, 20-/18-/16-bit SAR ADCs, including the
MAX11905 ADC family. Featuring a combination of wide
2.7V to 13.2V supply voltage range and wide 400MHz
bandwidth, the MAX44206 is suitable for low-power, high-
performance data acquisition systems.
The MAX44206 offers a VOCM input to adjust the output
common-mode voltage, eliminating the need for a cou-
pling transformer or AC-coupling capacitors. This adjust-
able output common-mode voltage allows the MAX44206
to match the input common-mode voltage range of the
ADC following it. Shutdown mode consumes only 6.8µA
and extends battery life in battery-powered applications
or reduces average power in systems cycling between
shutdown and periodic data readings.
The MAX44206 is available in an 8-pin μMAX® package
and is specified for operation over the -40°C to +125°C
temperature range.
Applications
Single-Ended to Differential Conversion
High-Speed Process Control
Medical Imaging
Fully-Differential Signal Conditioning
Active Filters
Features and Benets
Low Input Noise Drives Precision SAR ADCs
3.1nV/√Hz at 1kHz
200nVP-P from 0.1Hz to 10Hz
High Speed for DC and AC Applications
Gain-Bandwidth Product 400MHz
-3dB Gain-Bandwidth Product 180MHz
Slew Rate 180V/µs
Ultra-Low Distortion Drives AC Inputs to 20-Bit SAR
ADCs
HD2 = -141dB, HD3 = -152dB at fIN = 10kHz,
VOUT,DIFF = 2VP-P
HD2 = -106dB, HD3 = -115dB at fIN = 1MHz,
VOUT,DIFF = 2VP-P
Wide Supply Range (2.7V to 13.2V) Drives Unipolar
or Bipolar (±6.6V) Signals
3.7mA Quiescent Supply Current with Only 6.8µA
Shutdown Current
8-Pin μMAX Package Saves Board Space
Ordering Information appears at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
19-7446; Rev 0; 11/14
Typical Application Circuit
V
S+
V
S-
OUT+
OUT-
1kΩ
1kΩ
+5V
-5V
MAX44206
VOCM
INM
INP
VOCM
OUT-
OUT+
IN-
IN+
1kΩ
1kΩ
V
CM
-
-
+
V
INM
V
INP
+
-160
-140
-120
-100
-80
-60
-40
-20
0
10 100 1000 10000
MAGNITUDE (dB)
INPUT FREQUENCY (kHz)
HD2 AND HD3 vs. FREQUENCY
HD2,NO
LOAD
HD3,NO
LOAD
VS+ = +5V,VS- = -5V VOUTDIFF = 2VP-P
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
EVALUATION KIT AVAILABLE
VS+ to VS- .............................................................-0.3V to +15V
All Other Pins ................................. (VS-) - 0.3V to (VS+) + 0.3V
IN+ to IN- ..............................................................-0.3V to +0.3V
Continuous Input Current into Any Pin (Note 1) ...............±20mA
Output Short-Circuit Duration (Note 1) .................................. 10s
Continuous Power Dissipation (TA = +70°C)
µMAX (derate 10.3mW/°C above +70°C) ................824.7mW
Operating Temperature Range ......................... -40°C to +125°C
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) ....................................... +260°C
μMAX
Junction-to-Ambient Thermal Resistance JA) .......77.6°C/W
Junction-to-Case Thermal Resistance JC) .................5°C/W
(Note 1)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V (Note 2), RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER SUPPLY
Supply Voltage Range VS
VS+ to VS-, guaranteed by PSRR
(EP = VS-) 2.7 13.2 V
Quiescent Current IS
No load, RL = ∞ 3.7 6.8 mA
SHDN = 0V 6.8 20 µA
Power-Supply Rejection Ratio PSRR VS+ to VS- = 2.7V to 13.2V
(EP = VS-)90 123 dB
DIFFERENTIAL PERFORMANCE—DC SPECIFICATIONS
Input Common-Mode Range VICM Guaranteed by CMRR (VS-) + 1.1 (VS+) - 1.1 V
Input Common-Mode
Rejection Ratio CMRR VICM = (VS-) + 1.1V to (VS+) - 1.1V 94 130 dB
Input Offset Voltage VOS ±0.2 ±1.5 mV
Input Offset Voltage Drift TCVOS 0.2 µV/°C
Input Bias Current IB30 750 nA
Input Offset Current IOS ±15 ±350 nA
Open-Loop Gain AVOL VOUT,DIFF = 6.6VP-P , TA = +25°C 96 130 dB
Output Short-Circuit Current ISC 60 mA
Output Voltage Swing VS+ - VOUT Applies to VOUT+, VOUT 0.98 1.15 V
VOUT - VS- Applies to VOUT+, VOUT- 0.92 1.10
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
www.maximintegrated.com Maxim Integrated
2
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.maximintegrated.com/thermal-tutorial.
Absolute Maximum Ratings
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.
Package Thermal Characteristics
Electrical Characteristics (±5V Supply)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V (Note 2), RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DIFFERENTIAL PERFORMANCE—AC SPECIFICATIONS
Input Voltage-Noise Density eNf = 1kHz 3.1 nV/√Hz
Input Voltage Noise 0.1Hz < f < 10Hz 200 nVP-P
Input Current-Noise Density iNf = 1kHz 1.5 pA/√Hz
1/f Noise Due to Input Current 0.1Hz < f < 10Hz 220 pAP-P
-3dB Small-Signal Bandwidth VOUT,DIFF = 0.1VP-P 180 MHz
0.1dB Gain Flatness Bandwidth VOUT,DIFF = 0.1VP-P 25 MHz
-3dB Large-Signal Bandwidth VOUT,DIFF = 2VP-P 38 MHz
0.1dB Gain Flatness Bandwidth VOUT,DIFF = 2VP-P 19 MHz
Slew Rate (Differential) SR VOUT,DIFF = 2VP-P 180 V/µs
Capacitive Loading CLNo sustained oscillations 5 pF
HD2/HD3 Specications
VOUT,DIFF = 2VP-P, f = 10kHz -129/-146
dBc
VOUT,DIFF = 2VP-P, f = 1MHz -90/-98
VOUT,DIFF = 6.6VP-P, f = 10kHz -124/-142
VOUT,DIFF = 6.6VP-P, f = 1MHz -86/-90
Settling Time tS
Settling to 0.1%, VOUT,DIFF = 4VP-P 58 ns
Settling to 0.1%, VOUT,DIFF = 6.6VP-P 107
Output Impedance ROUT,DIFF fC = 1MHz 0.1
Output Balance Error VOUT,DIFF = 1VP-P, f = 1MHz -54 dB
SHDN INPUT
Input Voltage VIH 1.25 V
VIL 0.65
Input Current IIH VSHDN = 2V 0.2 1.5 µA
IIL VSHDN = 0V -1.5 -0.2
Turn-On Time tON Output condition 1.2 µs
Turn-Off Time tOFF Output condition 0.8 µs
VOCM INPUT to VOUT,CM PERFORMANCE
Input Voltage Range Guaranteed by gain parameter (VS-) + 1.2 (VS+) - 1.2 V
Output Common-Mode Gain GOCM ∆(VOUT,CM)/∆(VOCM), VOCM = (VS-) + 1.2
to (VS+) - 1.2 0.99 1 1.01 V/V
Input Offset Voltage ±13 ±38 mV
Input Bias Current -2 -0.30 µA
Output Common-Mode
Rejection Ratio (Note 4) OCMRR 2 x ∆(VOS,)/∆(VOCM), VOCM = (VS-) + 1.2
to (VS+) - 1.2 100 130 dB
-3dB Small-Signal Bandwidth VOUT,CM = 100mVP-P 16 MHz
Slew Rate VOUT,CM = 1VP-P 6 V/µs
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
www.maximintegrated.com Maxim Integrated
3
Electrical Characteristics (continued)
(VS+ = +5V, VS- = 0V, VOCM = 2.5V, SHDN = VS+, EP = 0V (Note 2), RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-),
TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER SUPPLY
Supply Voltage Range VS
VS+ to VS-, guaranteed by PSRR
(EP = VS-) 2.7 13.2 V
Quiescent Current IS
No load, RL = ∞ 3.7 6.8 mA
VSHDN = 0V 5.9 20 µA
DIFFERENTIAL PERFORMANCE—DC SPECIFICATIONS
Input Common-Mode Range VICM Guaranteed by CMRR (VS-) + 1.1 (VS+) - 1.1 V
Input Common-Mode
Rejection Ratio CMRR VICM = (VS-) + 1.1V to (VS+) - 1.1V 94 130 dB
Input Offset Voltage VOS ±0.2 ±1.5 mV
Input Offset Voltage Drift TC VOS 0.2 µV/°C
Input Bias Current IB30 750 nA
Input Offset Current IOS ±15 ±350 nA
Open-Loop Gain AVOL VOUT,DIFF = 2.8VP-P, TA = +25°C 95 120 dB
Output Short-Circuit Current ISC 60 mA
Output Voltage Swing VS+ - VOUT Applies to VOUT+, VOUT 0.95 1.1 V
VOUT - VS- Applies to VOUT+, VOUT 0.85 1.1
DIFFERENTIAL PERFORMANCE—AC SPECIFICATIONS
Input Voltage-Noise Density eNf = 1kHz 3.1 nV/√Hz
Input Voltage Noise 0.1Hz < f < 10Hz 200 nVP-P
Input Current-Noise Density iNf = 1kHz 1.5 pA/√Hz
1/f Noise Due to Input Current 0.1Hz < f < 10Hz 220 pAP-P
-3dB Small-Signal Bandwidth VOUT,DIFF = 0.1VP-P 180 MHz
0.1dB Gain Flatness Bandwidth VOUT,DIFF = 0.1VP-P 25 MHz
-3dB Large-Signal Bandwidth VOUT,DIFF = 2VP-P 38 MHz
0.1dB Gain Flatness Bandwidth VOUT,DIFF = 2VP-P 19 MHz
Slew Rate (Differential) SR VOUT,DIFF = 2VP-P 120 V/µs
Capacitive Loading CLNo sustained oscillations 5 pF
HD2/HD3 Specications VOUT = 4VP-P, f = 10kHz -123/-143 dBc
VOUT = 4VP-P, f = 1MHz -88.5/-95.5
Settling Time tS
Settling to 0.1%, VOUT,DIFF = 4VP-P 58 ns
Settling to 0.1%, VOUT,DIFF = 6.6VP-P 100
Output Impedance ROUT,DIFF fC = 1MHz (VOUT,DIFF) 0.1
Output Balance Error VOUT,DIFF = 1VP-P, f = 1MHz -52 dB
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
www.maximintegrated.com Maxim Integrated
4
Electrical Characteristics (+5V Supply)
(VS+ = +5V, VS- = 0V, VOCM = 2.5V, SHDN = VS+, EP = 0V (Note 2), RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-),
TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
Note 2: EP is the logic ground reference to the SHDN pin.
Note 3: All devices are 100% production tested at TA = +25°C. Temperature limits are guaranteed by design.
Note 4: OCMRR is mainly determined by external gain resistors matching. The formula used for OCMRR calculation assumes that
gain resistors are perfectly matched. Therefore, OCMRR = (1 + RF/RG) x ∆VOS/∆V(VOCM).
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SHDN INPUT
Input Voltage VIH 1.25 V
VIL 0.65
Input Current IIH VSHDN = 2V 0.2 1.5 µA
IIL VSHDN = 0V -1.5 -0.2
Turn-On Time tON Output condition 1.2 µs
Turn-Off Time tOFF Output condition 0.8 µs
VOCM INPUT to VOUT,CM PERFORMANCE
Input Voltage Range Guaranteed by gain parameter (VS-) +1.2 (VS+)-1.2 V
Output Common-Mode Gain GOCM ∆(VOUT,CM)/∆(VOCM), VOCM = (VS-) + 1.2
to (VS+) - 1.2 0.99 1 1.01 V/V
Input Offset Voltage ±13 ±38 mV
Input Bias Current -2 -0.3 µA
Output Common-Mode
Rejection Ratio (Note 4) OCMRR 2 x ∆(VOS,)/∆(VOCM),
VOCM = (VS-) + 1.2 to (VS+) - 1.2 90 130 dB
-3dB Small-Signal Bandwidth VOUT,CM = 100mVP-P 16 MHz
Slew Rate VOUT,CM = 1VP-P 6 V/µs
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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5
Electrical Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
-1500
-1300
-1100
-900
-700
-500
-300
-100
100
300
500
700
900
1100
1300
1500
-50 -25 025 50 75 100 125 150
VOS (µV)
TEMPERATURE C)
INPUT OFFSET VOLTAGE (IN+, IN-)
vs. TEMPERATURE (100 UNITS)
toc4
VS+ = +5V
VS- = -5V
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
02.5 57.5 10 12.5 15
SUPPLY CURRENT(mA)
SUPPLY VOLTAGE (V)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
toc01
TA= -40°C
TA= +25°C
TA= +125°C
200
220
240
260
280
300
-50 -25 025 50 75 100 125 150
INPUT OFFSET VOTLAGE (µV)
TEMPERATURE (°C)
INPUT OFFSET VOLTAGE (IN+, IN-)
vs. TEMPERATURE
Vs+ = +1.5V
Vs-= -1.5V
Vs+ = +5V
Vs-= -5V
Vs = +2.5V
Vs-= -2.5V
toc07
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4.6
-50 -25 025 50 75 100 125 150
SUPPLY CURRENT (mA)
TEMPERATURE (°C)
SUPPLY CURRENT
vs. TEMPERATURE toc02
VS+ = +5V
VS- = -5V
VS+ = +2.5V
VS- = -2.5V
VS+ = +1.5V
VS- = -1.5V
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-6 -4 -2 0246
INPUT OFFSET VOLTAGE VARIATION (mV)
VOCM (V)
INPUT OFFSET VOLTAGE VARIATION
vs. VOCM
toc08
TA= +25°C
TA= -40°C
TA= +125°C
5.8
6
6.2
6.4
6.6
6.8
7
7.2
-50 -25 025 50 75 100 125 150
SHUTDOWN SUPPLY CURRENT (µA)
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
toc03
VS+ = +5V
VS- = -5V
VS+ = +2.5V
VS- = -2.5V
-1.5
-1
-0.5
0
0.5
1
1.5
2
-1.6 -1.2 -0.8 -0.4 00.4 0.8 1.2 1.6
INPUT OFFSET VOLTAGE DRIFT
OVER TEMPERATURE (µV)
VICM (V)
INPUT OFFSET VOLTAGE CHANGE OVER
TEMPERATURE vs. VICM
Vs+ = +2.5V
Vs-= -2.5V
TA= -40°C
TA= +25°C
TA= +125°C
toc09a
0
2
4
6
8
10
12
-0.8 -0.6 -0.4 -0.2 00.2 0.4 0.6 0.8
OCCURRENCE (N)
INPUT OFFSET VOLTAGE (μV)
INPUT OFFSET VOLTAGE (IN+, IN-)
HISTOGRAM toc05
HISTOGRAM
TA = +25°C
200
220
240
260
280
2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5
INPUT OFFSET VOTLAGE (µV)
SUPPLY VOLTAGE (V)
IN+, IN-INPUT OFFSET VOLTAGE
vs. SUPPLY VOLTAGE
TA = +25°C
TA= -40°C
TA= +125°C
toc06
Maxim Integrated
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
-20
-10
0
10
20
30
40
50
60
33.2 3.4 3.6 3.8 44.2
OUTPUT VOCM ERROR OVER TEMPERATURE (mV)
INPUT VOCM VOLTAGE (V)
VOCM ERROR OVER TEMPERATURE
vs. VOCM INPUT
SUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -0.5V to +0.5VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -4V to +4V
V
S+
= +5V
V
S-
= -5V TA = -40˚C
TA= +25˚C
TA= +125˚C
toc11a
-20
-10
0
10
20
30
40
50
60
-4.2 -3 -1.8 -0.6 0.6 1.8 34.2
OUTPUT VOCM ERROR OVER TEMPERATURE (mV)
INPUT VOCM VOLTAGE (V)
VOCM ERROR OVER TEMPERATURE
vs. VOCM INPUT
SUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -0.5V to +0.5V
SUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -4V to +4V
Vs+ = +5V
Vs-= -5V T
A
= -40˚C
T
A
= +25˚C
T
A
= +125˚C
toc11a
INCREASED
SCALE
-1
-0.5
0
0.5
1
1.5
2
2.5
-0.4 -0.3 -0.2 -0.1 00.1 0.2 0.3 0.4
INPUT OFFSET VOLTAGE DRIFT
OVER TEMPERATURE (µV)
VICM (V)
INPUT OFFSET VOLTAGE CHANGE OVER
TEMPERATURE vs. VICM
VS+ = +1.35V
VS-= -1.35V
TA= -40°C
TA= +25°C
TA= +125°C
toc09b
SUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -0.5V to +0.5VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -1.5V to +1.5V
Vcc+ = +2.5V
Vcc- = -2.5V TA= -40˚C
TA= +25˚C
TA= +125˚C
toc11b
-20
-10
0
10
20
30
40
50
60
1.2 1.3 1.4 1.5 1.6
OUTPUT VOCM ERROR OVER TEMPERATURE (mV)
INPUT VOCM VOLTAGE (V)
VOCM ERROR OVER TEMPERATURE
vs. VOCM INPUT
SUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -0.5V to +0.5VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VSUPPLY VOLTAGE : 3VVOCM RANGE = -1.5V to +1.5V
Vcc+ = +2.5V
Vcc- = -2.5V
T
A
= -40˚C
T
A
= +25˚C
T
A
= +125˚C
toc11b
INCREASED
SCALE
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-4.2 -3 -1.8 -0.6 0.6 1.8 34.2
INPUT OFFSET VOLTAGE DRIFT
OVER TEMPERATURE (µV)
VICM (V)
INPUT OFFSET VOLTAGE CHANGE OVER
TEMPERATURE vs. VICM
Vs+ = +5V
Vs-= -5V
TA= -40˚C
TA= +25˚C
TA= +125˚C
toc09c
0
2
4
6
8
10
12
14
-25 -23 -21 -19 -17 -15 -13 -11 -9 -7 -5
OCCURRENCE (N)
OUTPUT COMMON-MODE VOLTAGE ERROR (mV)
OUTPUT COMMON-MODE
VOLTAGE ERROR HISTOGRAM
toc10
TA= +25˚C
VOCM = 0V
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
-20
-10
0
10
20
30
40
50
60
70
-4 -3 -2 -1 01234
INPUT BIAS CURRENT (nA)
INPUT COMMON-MODE RANGE VICM (V)
INPUT BIAS CURRENT (IN+/IN-)
vs. INPUT COMMON-MODE VOLTAGE
TA= -40˚C
TA= +125˚C
TA= +25˚C
toc13
-14
-13.8
-13.6
-13.4
-13.2
-13
-12.8
-12.6
-12.4
-12.2
-12
-50 -25 025 50 75 100 125 150
OUTPUT VOCM ERROR (mV)
TEMPERATURE (°C)
OUTPUT VOCM ERROR vs. TEMPERATURE
VOCM INPUT= 0V
Vs+ = +5V
Vs-= -5V
Vs+ = +2.5V
Vs-= -2.5V
toc12
-0.5
-0.45
-0.4
-0.35
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
-4.2 -3 -1.8 -0.6 0.6 1.8 34.2
VOCM INPUT BIAS CURRENT (µA)
INPUT VOCM VOLTAGE (V)
VOCM INPUT BIAS CURRENT
vs. VOCM INPUT VOLTAGE
toc16
TA = -40˚C
TA = +25˚C
TA = +125˚C
-200
-170
-140
-110
-80
-50
-20
10
40
70
100
-50 -25 025 50 75 100 125 150
INPUT BIAS CURRENT (nA)
TEMPERATURE (°C)
INPUT BIAS CURRENT (IN+/IN-)
vs. TEMPERATURE
VICM = 0V
toc14a
-150
-125
-100
-75
-50
-25
0
25
50
75
100
125
150
-50 -25 025 50 75 100 125 150
IOS (nA)
TEMPERATURE (°C)
INPUT OFFSET CURRENT (IN+/IN-) vs.
TEMPERATURE (100 UNITS)
toc14b
0
5
10
15
20
25
30
35
-50 -40 -30 -20 -10 010 20 30 40 50
OCCURRENCE (N)
INPUT OFFSET CURRENT (nA)
INPUT OFFSET CURRENT HISTOGRAM
toc15
TA= +25˚C
-0.45
-0.4
-0.35
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
-50 -25 025 50 75 100 125 150
VOCM INPUT BIAS CURRENT (µA)
TEMPERATURE (°C)
VOCM INPUT BIAS CURRENT
vs. TEMPERATURE
toc17
VOCM = 0V
VOCM = 4V
VOCM = 3.5V
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
Typical Operating Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
0
0.2
0.4
0.6
0.8
1
1.2
-50 -25 025 50 75 100 125 150
OUTPUT VOLTAGE HIGH VOH (V)
TEMPERATURE (C)
VOH vs. TEMPERATURE
vs. LOAD RESISTOR
RLOAD = 1k
RLOAD = 10k
RLOAD = 1k
RLOAD = 10k
RLOAD = 1k
RLOAD = 10k
RLOAD = 200
RLOAD = 1k
RLOAD = 10k
toc18b
Vs+ = +2.5V
Vs-= -2.5V
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
-50 -25 025 50 75 100 125 150
OUTPUT VOLTAGE HIGH VOH (V)
TEMPERATURE (
C)
VOH vs. TEMPERATURE
vs. LOAD RESISTOR
RLOAD = 1k
RLOAD = 200
RLOAD = 10k
toc18c
Vs+ = +5V
Vs-= -5V
0
0.2
0.4
0.6
0.8
1
1.2
-50 -25 025 50 75 100 125 150
OUTPUT VOLTAGE HIGH VOL (V)
TEMPERATURE (
C)
VOL vs. TEMPERATURE
vs. LOAD RESISTOR
RLOAD = 1k
RLOAD = 200
RLOAD = 10k
toc19a
Vs+ = +1.5V
Vs-= -1.5V
0
0.2
0.4
0.6
0.8
1
1.2
-50 -25 025 50 75 100 125 150
OUTPUT VOLTAGE HIGH V
OH
(V)
TEMPERATURE (°C)
VOH vs. TEMPERATURE
vs. LOAD RESISTOR
RLOAD = 200
RLOAD = 1k
RLOAD = 10k
RLOAD = 200
RLOAD = 1k
RLOAD = 10k
RLOAD = 200
R
LOAD
= 1k
R
LOAD
= 10k
R
LOAD
= 200
toc18a
Vs+ = +1.5V
Vs-= -1.5V
0
0.2
0.4
0.6
0.8
1
1.2
-50 -25 025 50 75 100 125 150
OUTPUT VOLTAGE HIGH VOH (V)
TEMPERATURE (
C)
VOL vs. TEMPERATURE
vs. LOAD RESISTOR
RLOAD = 1k
RLOAD = 200
RLOAD = 10k
toc19b
Vs+ = +2.5V
Vs-= -2.5V
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
-50 -25 025 50 75 100 125 150
OUTPUT VOLTAGE HIGH VOH (V)
TEMPERATURE (
C)
VOL vs. TEMPERATURE
vs. LOAD RESISTOR
RLOAD = 1k
RLOAD = 200
RLOAD = 10k
toc19c
SHORT-CIRCUIT PROTECTION OCCURS AT
RLOAD = 200at 125°C
-300
-250
-200
-150
-100
-50
0
-50 -25 025 50 75 100 125 150
SHDN INPUT CURRENT (nA)
TEMPERATURE (°C)
SHDN INPUT CURRENT
vs. SHDN VOLTAGE vs. TEMPERATURE
toc20a
VSHDN = 0V
0
50
100
150
200
250
300
350
-50 -25 025 50 75 100 125 150
SHDN INPUT CURRENT (nA)
TEMPERATURE (°C)
SHDN INPUT CURRENT
vs. SHDN INPUT VOLTAGE
toc20b
VSHDN = 2V
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
0
5
10
15
20
25
2.5 4.5 6.5 8.5 10.5 12.5
INPUT OFFSET VOLTAGE (uV)
SUPPLY VOLTAGE (V)
INPUT OFFSET VOLTAGE
vs. SUPPLY VOLTAGE
toc22
40
50
60
70
80
90
100
-50 -25 025 50 75 100 125 150
SHORT-CIRCUIT CURRENT (mA)
TEMPERATURE (°C)
OUTPUT SHORT-CIRCUIT CURRENT
vs. TEMPERATURE
toc23a
Vs+ = +5V
Vs-= -5V
Vs+ = +2.5V
Vs-= -2.5V
VOCM = 0V,
VIN+ = VIN-= 0V,
OUT+ SHORTED TO VS-
-80
-70
-60
-50
-40
-30
-50 -25 025 50 75 100 125 150
SHORT-CIRCUIT CURRENT (mA)
TEMPERATURE (°C)
OUTPUT SHORT-CIRCUIT CURRENT
vs. TEMPERATURE
toc23b
Vs+ = +5V
Vs-= -5V
Vs+ = +2.5V
Vs-= -2.5V
VOCM = 0V,
VIN+ = VIN-= 0V,
OUT+ SHORTED TO VS+
0.9
0.91
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
-50 -25 025 50 75 100 125 150
SHDN INPUT THRESHOLD VOLTAGE (V)
TEMPERATURE (°C)
SHDN INPUT THRESHOLD VOLTAGE
vs. TEMPERATURE toc21a
VSHDNTH+
VSHDNTH-
Vs+ = +5V
Vs-= -5V
0.9
0.91
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
-50 -25 025 50 75 100 125 150
SHDN INPUT THRESHOLD VOLTAGE (V)
TEMPERATURE (°C)
SHDN INPUT THRESHOLD VOLTAGE
vs. TEMPERATURE
toc21b
VSHDNTH+
VSHDNTH-
Vs+ = +2.5V
Vs-= -2.5V
Maxim Integrated
10
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
SMALL-SIGNAL GAIN vs. FREQUENCY
VOUTDIFF = 0.1VP-P
VS+ = +5V,
VS- = -5V
toc25
-20
-15
-10
-5
0
5
10
15
20
25
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
LARGE-SIGNAL GAIN vs. FREQUENCY
VOUTDIFF = 2VP-P
GAIN = 1V/V
VOCM = 0V
toc28
VOUTDIFF = 2VP-P
GAIN = 10V/V
VOCM = 0V
-16
-14
-12
-10
-8
-6
-4
-2
0
2
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
LARGE-SIGNAL GAIN vs. FREQUENCY
V
OUTDIFF
= 2V
P-P,
V
OCM
= 1.65V
GAIN = 1V/V
toc29
-40
-30
-20
-10
0
10
20
30
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
SMALL-SIGNAL GAIN vs. FREQUENCY
VOUTDIFF = 0.1VP-P
GAIN = 1V/V
VOUTDIFF = 0.1VP-P
GAIN = 10V/V
toc24
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
LARGE-SIGNAL GAIN vs. FREQUENCY
CF=10pF
VOUTDIFF = 2VP-P
CF= NO CAP, 10pF
CF is Feedback Capacitor
CF= NO LOAD
toc30
-25
-20
-15
-10
-5
0
5
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
SMALL-SIGNAL GAIN vs. FREQUENCY
VOUTDIFF = 0.1VP-P
VOCM = 1.65V (BLACK TRACE),
VOCM = 0V (RED TRACE)
toc26
-25
-20
-15
-10
-5
0
5
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
SMALL-SIGNAL GAIN vs. FREQUENCY
ENTER TEXT
HERE
VOUTDIFF = 0.1VP-P
CLOAD = 10pF (BLACK TRACE),
CLOAD = NO LOAD (RED TRACE)
toc27
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
-70
-60
-50
-40
-30
-20
-10
0
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
OUTPUT BALANCE ERROR vs. FREQUENCY
toc34
VIN = 1VP-P
VS+ = +2.5V
VS-= -2.5V
VS+ = +5V
VS-= -5V
-30
-25
-20
-15
-10
-5
0
5
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
LARGE-SIGNAL GAIN vs. FREQUENCY
toc31
VOUTDIFF = 2VP-P
CLOAD = 0pF, 10pF
-130
-110
-90
-70
-50
-30
-10
0.01 1100 10000
MAGNITUDE (dB)
FREQUENCY (kHz)
PSRR+ vs. FREQUENCY
toc37
VS+ = +5V
VS-= -5V
PSRR-
PSRR+
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
LARGE-SIGNAL GAIN FLATNESS
vs. FREQUENCY toc32
VOUTDIFF = 0.5VP-P
VOUTDIFF = 2VP-P
VOUTDIFF = 1VP-P
0
20
40
60
80
100
120
140
160
180
200
-10
0
10
20
30
40
50
60
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
UNITY-GAIN BANDWIDTH AND PHASE
vs. FREQUENCY toc38
RF= 1k, RG= 10
PHASE (radians)
GAIN
PHASE
CROSSOVER POINT:
GAIN = 0
FREQUENCY = 400MHz
PHASE = 87°(rad)
-60
-50
-40
-30
-20
-10
0
10
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
VOCM RESPONSE vs. FREQUENCY
toc33
BLACK TRACE:
VOCMIN = 100mVP-P
RED TRACE:
VOCMIN = 10mVP-P
1
10
100
0.1 110 100 1000 10000 100000
INPUT VOLTAGE-NOISE DENSITY (nV/√Hz)
FREQUENCY (Hz)
INPUT VOLTAGE-NOISE DENSITY
vs. FREQUENCY
toc39
-140
-120
-100
-80
-60
-40
-20
0
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
INPUT AC CMRR vs. FREQUENCY
toc35
VIN = 1VP-P
RF= 1k, RG= 10
BLACK
TRACE
VS+ = +2.5V
VS-= -2.5V
RED TRACE
VS+ = +5V
VS-= -5V
-70
-60
-50
-40
-30
-20
-10
0
10
20
0.01 1100 10000 1000000
MAGNITUDE (dB)
FREQUENCY (kHz)
VOCM OUTPUT AC CMRR
vs. FREQUENCY toc36
VIN = 1VP-P
BLACK
TRACE
VS+ = +2.5V
VS-= -2.5V
RED
TRACE
VS+ = +5V
VS-= -5V
RF= RG = 1kMATCHED 0.1% RESISTORS
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
-160
-140
-120
-100
-80
-60
-40
-20
0
10 100 1000 10000
MAGNITUDE(dB)
INPUT FREQUENCY (kHz)
HD2,1K load
HD2 AND HD3 vs. FREQUENCY
(VOUTDIFF = 4VP-P)
toc43
HD3,1K load
HD2,no load
HD3,No load
1
10
100
0.1 110 100 1000 10000 100000
INPUT CURRENT-NOISE DENSITY (pA/√Hz)
FREQUENCY (Hz)
INPUT CURRENT
-
NOISE SPECTRAL DENSITY
vs. FREQUENCY
toc40
-160
-140
-120
-100
-80
-60
-40
-20
0
12.4 3.8 5.2 6.6
MAGNITUDE(dB)
OUTPUT VOLTAGE SWING(Vp-p)
fIN = 11.5MHz
HD3 vs. OUTPUT SWING
toc46
fIN = 1MHz
fIN = 100kHz
fIN = 10kHz
-160
-140
-120
-100
-80
-60
-40
-20
0
10 100 1000 10000
MAGNITUDE(dB)
INPUT FREQUENCY (kHz)
HD2,1K load
HD2 AND HD3 vs. FREQUENCY
(V
OUTDIFF
= 1V
P-P
)
toc41
HD3,1K load
HD2,No load
HD3,No load
-150
-100
-50
0
50
100
150
INPUT VOLTAGE NOISE (nVP-P)
4s/div
0.1Hz to 10Hz INPUT VOLTAGE NOISE
toc47
0.1Hz TO 10Hz INPUT VOLTAGE NOISE: 200nVP-P
-160
-140
-120
-100
-80
-60
-40
-20
0
10 100 1000 10000
MAGNITUDE(dB)
INPUT FREQUENCY (kHz)
HD2,1K load
HD2 AND HD3 vs. FREQUENCY
(V
OUTDIFF
= 2V
P-P
)
toc42
HD3,1K load
HD2,no load
HD3,No load
-150
-100
-50
0
50
100
150
INPUT CURRENT NOISE (pAP-P)
4s/div
INPUT CURRENT NOISE 0.1Hz to 10Hz
toc48
INPUT CURRENT NOISE = 220pAP-P
-160
-140
-120
-100
-80
-60
-40
-20
0
10 100 1000 10000
MAGNITUDE(dB)
INPUT FREQUENCY (kHz)
HD2,1K load
HD2 AND HD3 vs. FREQUENCY
(VOUTDIFF = 6.6VP-P)
toc44
HD3,1K load
HD2,no load
HD3,No load
-140
-120
-100
-80
-60
-40
-20
0
12.4 3.8 5.2 6.6
MAGNITUDE (dB)
OUTPUT VOLTAGE SWING (VP-P)
fIN = 11.5MHz
HD2 vs. OUTPUT SWING
toc45
fIN = 1MHz
fIN = 100kHz
fIN =1 0kHz
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
(VS+ = +5V, VS- = -5V, VOCM = 0V, SHDN = VS+, EP = 0V, RF = RG = 1kΩ, RL = 1kΩ (between OUT+ and OUT-), TA = -40°C to +125°C,
unless otherwise noted.)
SMALL-SIGNAL RESPONSE
100mV/div
100mV/div
toc49
50ns/div
VINDIFF
VOUTDIFF
CLOAD = 10pF
OUTPUT-TRANSIENT RESPONSE
vs. SHUTDOWN PULSE
2V/div
1V/div
toc53a
5µs/div
VSHDN
VOUT-
LARGE-SIGNAL TRANSIENT RESPONSE
500mV/div
500mV/div
toc50a
50ns/div
V
INDIFF
V
OUTDIFF
C
LOAD
= 10pF
LARGE-SIGNAL TRANSIENT RESPONSE
500mV/div
500mV/div
toc50b
50ns/div
VINDIFF
VOUTDIFF
OUTPUT+ TRANSIENT RESPONSE
vs. SHUTDOWN PULSE
2V/div
1V/div
toc53b
5µs/div
VSHDN
VOUT+
5µs/div
VOCM SMALL-SIGNAL
TRANSIENT RESPONSE
100mV/div
100mV/div
toc51
100ns/div
VOCM
VOUT+
VOCM LARGE-SIGNAL
TRANSIENT RESPONSE
2V/div
2V/div
toc52
500ns/div
VOCM
VOUT+
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MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1 IN- Inverting Input
2 VOCM Output Common-Mode Voltage Input
3 VS+ Positive Supply Voltage Input
4 OUT+ Noninverting Differential Output
5 OUT- Inverting Differential Output
6 VS- Negative Supply Voltage Input
7SHDN Shutdown Mode Input (Active-Low). SHDN is referred to the exposed pad.
8 IN+ Noninverting Input
EP Exposed Pad. EP is the logic ground reference to the SHDN pin.
1
2
3
4
8
7
6
5
IN+
SHDN
V
S-
OUT-
*EP = EXPOSED PAD
*
OUT+
V
S+
VOCM
IN-
µMAX
TOP VIEW
MAX44206
+
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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15
Pin Conguration
Pin Description
Detailed Description
The MAX44206 is a low-noise, low-power, very low-dis-
tortion fully differential (input and output) op amp capable
of driving high-resolution 16-/18-/20-bit SAR ADCs with
input signal frequencies from DC to 1MHz. These high-
resolution signal chain ICs are used in test and measure-
ment applications, as well as medical instrumentation and
industrial control systems.
This fully differential op amp accepts either single-ended
or fully differential input signals at its inputs and con-
verts the input signal into fully differential outputs that
are exactly equal in amplitude and 180° apart in phase.
Ideally, the noise and distortion performance of the ampli-
fier should match or exceed the linearity of the ADC to
preserve the overall system accuracy.
Four precisely matched resistors (two for feedback and
two for gain setting) set the differential closed-loop gain
as shown in the Functional Diagram.
The MAX44206 has an output voltage common-mode
(VOCM) input to set the DC common-mode voltage level
of the differential outputs without affecting the balance
of the AC differential output signal on each output. The
MAX44206 also features a low-power shutdown mode
that consumes only 6.8µA of supply current from the VS+
pin. Note that while the outputs are high impedance dur-
ing shutdown, the feedback networks may provide paths
for current to flow from the input source(s).
C
C
OUT+
VOCM
OUT-
V
S-
V
S+
SHDN
OUTPUT
STAGE
COMMON-MODE
FEEDBACK
GAIN
STAGE
IN+
IN-
MAX44205
VOCM INPUT
R
F
R
G
R
F
INN
INP
OUTPUT
STAGE
C
C
INPUT
STAGE
R
G
GAIN
STAGE
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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16
Functional Diagram
Terminology and Denitions
Differential Voltage
The differential voltage at the input is the voltage applied
across INP to INM and the differential voltage at the out-
put is the voltage across OUT+ to OUT-. Equations for
input and output differential voltages are listed below:
VIN,dm = (VINP - VINM)
VOUT,dm = (VOUT+ - VOUT-)
VOUT+ and VOUT- are voltages at the OUT+ and OUT-
terminals with respect to output common-mode voltage
set by the VOCM input voltage.
Common-Mode Voltage
The common-mode voltage at the input is the average
of the input pins (IN+ and IN-) and at the output, it is the
average of two outputs. Equations for input and output
common-mode voltages are listed below:
VIN,cm = (VIN+ + VIN-)/2
VOUT,cm = VOCM = (VOUT+ + VOUT-)/2
Though it was mentioned that the input common-mode
voltage is the average of the voltage seen on both input
pins, the range is slightly different depending on if the
input signal is fully differential or single ended.
For fully differential input applications, where VINP =
-VINM, the common-mode input voltage is:
VIN,cm = (VIN+ +VIN-)/2 VOCM x RG/(RF + RG)
+ VCM x RF/(RF + RG)
With single-ended input applications, there will be an
input signal component to the input common-mode volt-
age, as there is no out-of-phase signal not applied on the
other input. Applying VINP (connecting VINM to zero), the
common-mode input voltage is:
VIN,cm = (VIN+ + VIN-)/2 VOCM x RG/(RF + RG) +
VCM x RF/(RF + RG) + VINP/2 x RF/(RF + RG)
Common-Mode Offset Voltage
The common-mode offset voltage is defined as the differ-
ence between the voltage applied to the VOCM terminal
and the output common-mode voltage.
VOS,cm = (VOUT,cm - VOCM)
Input Offset Voltage, CMRR, and VOCM CMRR
Input offset voltage is the differential voltage error (VOS,dm)
between the input pins (IN+ and IN-). CMRR performance
is affected by both the input offset voltage error at the input
due to change in input common-mode voltage (VIN_,cm)
and the change in input offset voltage VOS,dm) due to
VOCM change. So, there are two CMRR terms:
CMRRVIN,cm = ∆(VIN_,cm)/∆(VOS,dm)
CMRRVOCM = ∆(VOCM)/∆(VOS,dm)
The output common-mode rejection ratio is strongly
affected by the matching of gain-setting feedback network.
Output Balance Error
An ideal differential output implies the two outputs of the
amplifier should be exactly equal in amplitude but 180°
apart in phase. Output balance is the measure of how well
the outputs are balanced and is defined as the ratio of the
output common-mode voltage to the output differential
signal. It is generally expressed as dB in log scale.
Output Balance Error = 20 x log|(VOUT,cm)/(VOUT,dm)|
Operation and Equations
The Functional Diagram details the internal architecture
of the differential op amp. The negative feedback loop
across the outputs to respective inputs force voltages on
IN+ and IN- pins equal to each other. That implies:
OUT
INP
FG
OUT
INN
FG
V
V
RR
V
V
RR
+
=
=
From above equations see the relationship between dif-
ferential output voltage and inputs.
F
OUT OUT INP INN
G
R
(V V ) (V V ) R
+−
=−×
Figure 1. Differential Input, Differential Output Configuration
(Decoupling Capacitors Not Shown for Simplicity)
OUT+
V
S+
V
S-
OUT+
OUT-
R
F
R
F
+5V
-5V
MAX44206
VOCM
R
G
R
G
INM
INP
VOCM
OUT-
IN-
IN+
SHDN
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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17
The VOCM input voltage with the help of the common-
mode feedback circuit drives the output common-mode
voltage level to VOCM. This results in the following output
relations:
OUT,DM
OUT
OUT,DM
OUT
V
(V ) (VOCM) 2
V
(V ) (VOCM)
2
+
= +
=
Input and ESD Protection
As shown in Figure 2, ESD diodes are present on all the
pins with respect to the VS+ and VS- pins so that these
ESD diodes turn on and protect the part when voltages on
these pins go out of range from either supplies by more
than one diode drop. There are two series input resistors
and back-to-back diode protection between the inputs for
protection against excessive differential voltages across
the amplifier’s inputs.
SHDN and Exposed Pad
Shutdown Operation
The MAX44206 offers a shutdown mode for low-power
operation. Drive SHDN below 0.65V with respect to the
µMAX exposed pad (EP) to shut down the part and only
6.8µA (typ) will be drawn from VS+. To keep the part
active, SHDN needs to be at least 1.25V above EP.
Exposed Pad
EP is the logic ground reference to the SHDN pin. EP
should be connected to the PCB ground plane for opti-
mum thermal dissipation.
Figure 2. Showing ESD Protection Scheme in MAX44206
OUT+
VOCM
OUT-
V
S-
IN-
MAX44206
IN+
25
25V
S+
V
S-
ESD
CORE
CLAMP
V
S+
SHDN
D1
D1
V
S+
V
S-
D1
D1
V
S+
V
S-
D1
D1
D1
D1
V
S+
V
S-
D1
D1
V
S+
V
S-
D1
D1
V
S-
D1
D1
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
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Shutdown Operation with External
Components and Stimuli
In shutdown mode, quiescent supply current is low.
However, there will be currents flowing into the IC pins
depending on the external components and applied sig-
nals. Figure 3 shows the block diagram with these current
paths and Figure 2 shows internal protection devices. In
active operation mode (shutdown disabled), input signals
are applied to INP and INN. The voltage applied to the
VOCM pin sets the output common-mode voltage.
In shutdown mode, the voltages applied to INP, INN, and
VOCM will interact with the IC internal components result-
ing in current flowing into the IC pins. It must be noted
that the op amp’s outputs, OUT+ and OUT-, exhibit high-
impedance state in shutdown mode.
Figure 3. Currents Flowing when MAX44206 is in Shutdown
OUT+
VOCM
OUT-
VS-
IN-
MAX44206
IN+
25
25VS+
VS-
ESD
CORE
CLAMP
VS+ SHDN
D1
D1
VS+
VS-
D1
D1
VS+
VS-
D1
D1
D1
D1
VS+
VS-
D1
D1
VS+
VS-
D1
D1
VS-
D1
D1
INPUT
STAGE
CC
OUTPUT
OUTPUT
GAIN
COMMON-
MODE
FEEDBACK
VOCM
INPUT
I
VOCM
R
F
R
F
R
G
R
G
INP
INN
I
INN
I
INP
CC
GAIN
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
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Applications Information
The fully differential op amp is shown in Figure 4 for ref-
erence. Fully differential op amps provide a lot of advan-
tages, including rejecting common-mode noise coupled
to the input, the output, and from the power supply. The
effective output swing is increased by a factor of two
as the outputs are equal in amplitude and 180° apart in
phase.
For example, by applying a fully differential input signal of
1VP-P across INP and INN on Figure 1 there is a 1VP-P
differential output voltage swing. Another advantage of
having fully differential outputs is that even order harmon-
ics will be suppressed at the output.
Input Impedance Mismatch Due
to Source Impedance
The impedance looking into the IN+ and IN- nodes of
Figure 5 depends on how the inputs are driven. For a
fully differential input signal, i.e., VINP = VINM + 180°. The
input impedance looking into inputs is shown in Figure 5.
RINP = RINM = RG
For a single-ended input signal, since the inputs are not
balanced, the input impedance actually increases relative
to the fully differential case. The input impedance looking
into either input is:
G
INP INM F
GF
R
RR R
1
[1 ]
2 (R R )
= = 
−×
 +

Apart from the single-ended input and differential input
signal cases, an input signal source from a nonzero
source impedance may cause imbalance between feed-
back resistor networks for single-ended input driving case
as shown in the Figure 6. A terminating resistor RT as
shown in Figure 6 is used to impedance match to the
source such that:
S
T INM
INM S
R
RR RR
= ×
Figure 4. Fully Differential Op Amp Figure 5. Showing Fully Differential Architecture
V
S+
V
S-
OUT+
OUT-
V
S+
V
S-
MAX44206
VOCM
IN-
IN+
VOCM
OUT-
OUT+
DIFFERENTIAL STRUCTURE AT INPUT, OUTPUT REJECTS COUPLED
NOISE AT THE INPUT, OUTPUT AND AT THE POWER SUPPLY
V
S+
V
S-
OUT+
OUT-
+5V
-5V
MAX44206
VOCM
INM
INP
VOCM
OUT-
OUT+
IN-
IN+
R
G
R
G
R
F
R
F
V
CM
-
+
-
+
V
INM
V
INP
R
INP
R
INM
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
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A terminating resistor is inserted to correct for impedance
mismatch between the source and input. The gain resis-
tor mismatch across feedback networks is created due to
the parallel combination of RT and RS. So, to balance out
the gain resistor mismatch on the other input, insert RB
such that:
S
BT
TS
R
RRRR
= ×
Effects of Input Resistor Mismatch
If there is a mismatch between the feedback resistor (RF)
pair and gain resistor (RG) pair, there will be a small delta
in the feedback factor across the input pins. This delta in
the feedback factor is a source of common-mode error.
To apply an AC CMRR test without a differential input
signal, the common-mode rejection is proportional to
the resistor mismatch. Using 0.1% or better resistors will
mitigate most of the problems and will yield good CMRR
performance.
Noise Calculations
The MAX44206 offers input voltage and current noise
densities of 3.1nV/√Hz and 1.5pA/√Hz, respectively. From
Figure 7, the total output noise is a combination of noise
generated by the amplifier and the feedback and gain
resistors. The total output noise generated by both the
amplifier and the feedback components is given by the
equation:
22
F
n nF
G
nt
22
F
nRG nRF
G
R
[e (1 )] 2 (i R )
R
eR
2 (e ) 2 (e )
R
×+ ×
=
× + ×
ent is total output noise of the circuit shown in Figure 7
en is the input voltage-noise density
in is the input current-noise density
enRG is the noise voltage density contributed by the gain
resistor RG
enRF is the noise voltage density contributed by the feed-
back resistor RF
Resistor Noise =
4kTR f× × × ×∆
in nV/√Hz
T is absolute temperature in Kelvin
k is Boltzmann constant: k = 1.38 x 10-23 in joules/Kelvin
R is resistance in ohms and ∆f is frequency range in Hertz
The MAX44206 input-referred voltage noise contributes
the equivalent noise of a 600Ω resistor. For low noise,
keep the source and feedback resistance at or below this
value, i.e. RS + RG//RF ≤ 600Ω. At combinations of below
600Ω, amplifier noise is dominant, but in the region 600Ω
to 10kΩ, the noise is dominated by resistor thermal noise.
Any larger resistances beyond that, the noise current mul-
tiplied by the total resistance dominated the noise.
Figure 6. Compensation for Source Impedance
Figure 7. Fully Differential Amplifier
OUT-
OUT+
VS+
VS-
OUT+
OUT-
RF
VS+
VS-
MAX44206
VOCM
RG
VOCM
IN-
IN+
RS
RT
RB = RS//RT
RINM
RG
RF
VINM
SIGNAL
GENERATOR
VS+
VS-
OUT+
OUT-
RF
RF
+5V
-5V
MAX44206
VOCM
RG
RG
INM
INP
VOCM
OUT-
OUT+
IN-
IN+
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
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Lower resistor values are ideal for low-noise performance
at the cost of increased distortion due to increased load-
ing of the feedback network on the output stage. Higher
resistor values will yield better distortion performance
due to less loading on the output stage but at the cost of
increase in higher output noise.
Improving Stability Using
Feedback Capacitors
When the MAX44206 is configured such that a combina-
tion of parasitic capacitances at the inverting input form
a pole whose frequency lies within the closed-loop band-
width of the amplifier, a feedback capacitor across the
feedback resistor is needed to form a zero at a frequency
close to the frequency of the parasitic pole to recover the
lost phase margin.
Adding larger value feedback capacitors will reduce the
peaking of the amplifier but decreases the closed-loop
-3dB bandwidth.
Layout and Bypass Capacitors
For single-supply applications, it is recommended to place
a 0.1µF NPO or C0G ceramic capacitor within 1/8th of
an inch from the VS+ pin to ground and to also connect
a 10µF ceramic capacitor within 1 inch of the VS+ pin to
GND.
In dual-supply applications, it is recommended to install
0.1µF NPO or C0G ceramic capacitor within 1/8th of an
inch from the VS+ and VS- pins to GND and place 10µF
ceramic capacitors within 1 inch of the VS+ and VS- pins
to GND. Low ESR\ESL NPO capacitors are recommend-
ed for 0.1µF or smaller decoupling capacitors. A 0.1µF or
0.22µF capacitor is a good choice close to VOCM input
pin to ground.
Signal routing into and out of the part should be direct
and as short as possible into and out of the op amp
inputs and outputs. The feedback path should be carefully
routed with the shortest path possible without any para-
sitic capacitance forming between feedback trace and
board power planes. Ground and power planes should be
removed from directly under the amplifier input and output
pins. Also, care should be taken such that there will be no
parasitic capacitance formed around the summing nodes
at the inputs that could affect the phase margin of the part.
Any load capacitance beyond a few picofarads needs to
be isolated using series output resistors placed as close
as possible to the output pins to avoid excessive peaking
or instability.
Driving a Fully Differential ADC
The MAX44206 was designed to drive fully differential
SAR ADCs such as the MAX11905. The MAX11905 is
part of a family of 20-/18-/16-bit, 1.6Msps/1Msps ADCs
that offer excellent AC and DC performance. Figure 8
details a fully differential input to the MAX44206, which
then drives the fully differential MAX11905 ADC inputs
through the ADC input filter shown in the dashed box.
The MAX6126 provides a 3V reference output voltage,
which is fed to the ADC’s reference. The MAX44206’s
common mode (VOCM) is created by dividing down the
reference voltage by a factor of two. A pair of 1kΩ 0.1%
resistors are used for this purpose. The VOCM input is
bypassed to GND with a combination of 2.2µF (X7R) and
0.1µF (NPO) capacitors.
The MAX44206 is connected in a unity-gain configuration.
The input resistors and feedback resistors are all 1kΩ
0.1% resistors. The feedback resistors are bypassed by
a pair of 4.7nF (C0G, 100V) capacitors. These feedback
components roll the amplifier off to about 60MHz corner
frequency.
The ADC input filter uses a pair of 10Ω 0.1% resistors
and a 2.2nF (C0G) capacitor. This input filter assists the
MAX44206’s settling response with the MAX11905’s fast
acquisition window.
Figure 8 was used to test the AC performance in Figures
9 and 10. Data were taken with the input frequencies
at 10kHz on the MAX11905 Evaluation Kit. Figures 9
to 13 detail the results of the MAX11905 Evaluation Kit
(MAX11905DIFEVKIT#) GUI.
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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Figure 8. MAX44206 Driving a 20-Bit MAX11905 SAR ADC
V
S+
V
S-
OUT+
OUT-
100.1%
100.1%
2.2nF
COG
+5V
-5V
MAX44206
VOCM MAX11905
MAX6126
OUT
V
REFIN
A
VDD
GND
GND
IN
3V
3.3V
3.2V TO 12.6V
A
IN+
A
IN-
10µF
1.5V
0.1µF
4.7nF
C0G
-
+
+
-
V
CM
V
SIG
V
SIG
1kΩ
0.1%
1kΩ
0.1%
1kΩ
0.1%
1kΩ
0.1%
1kΩ
0.1%
1kΩ
0.1%
2.2µF
X7R
REFV
DD
ADC INPUT FILTER
3.3V
SHDN
4.7nF
C0G
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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The sample rate for Figure 9 is 1Msps and the sample
rate for Figure 10 is 1.6Msps, the MAX11905’s maximum
sample rate. As measured at the MAX11905 output, the
signal-to-noise ratio is > 97dB for both sample rates, with
total harmonic distortion > 112.9dB.
Figures 11 to 13 detail the DC performance of the
MAX44206 and MAX11905. These three figures detail
the results of shorting the inputs together to GND at the
VSIG sources and measuring the noise histogram at the
output of the ADC. All data was measured at 1Msps, with
65,536 samples taken. Figure 11 shows the results at a
20-bit code level with no averaging. Effective number of
bits (ENOB) is 17.9 bits.
One technique to improve a system’s ENOB is to aver-
age multiple samples. The tradeoff is a reduced effective
sample rate. The theoretical expected results of averag-
ing are a 0.5 improvement in ENOB for every average
factor of 2. Therefore, averaging by 16x should improve
ENOB by 2 bits. Figure 12 details this example, and the
ENOB is improved nearly 2 bits, from 17.9 bits to 19.8
bits. This shows that the noise from the ADC and the op
amp are not limiting the ENOB.
Figure 13 shows the results of averaging by 64x, which
will limit the effective sample rate to 15.6ksps (1Msps/64).
ENOB is 20.8 bits in this mode, making the MAX11905 a
lower power alternative to high-speed 24-bit delta-sigma
ADCs.
Figure 9. MAX11905 FFT (fSAMPLE = 1Msps, fIN = 10kHz)
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
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Figure 10. MAX11905 FFT (fSAMPLE = 1.6Msps, fIN = 10kHz)
Figure 11. MAX11905 Output Data Histogram (Inputs Shorted, Averaging = 1, fSAMPLE = 1Msps)
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
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Figure 12. MAX11905 Output Data Histogram (Inputs Shorted, Averaging = 16, fSAMPLE = 1Msps)
Figure 13. MAX11905 Output Data Histogram (Inputs Shorted, Averaging = 64, fSAMPLE = 1Msps)
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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Figure 14. MAX44206 Used to Drive a Single-Ended Input into a Differential, 20-Bit SAR ADC
3.2V to 12.6V
VS+
VS-
OUT+
OUT-
10
10
1kΩ
0.1%
499
0.1%
2.2nF
+5V
MAX44206
VOCM
MAX11905
MAX6126
OUT
VREF AVDD
GND
GND
IN
3V
3.3V
AIN+
AIN-
10µF
1.5V
0.1µF
+
-
6VP-P + 0VDC
3V
-3V
0V
0V
3V
1.5V
3V
0V
1.5V
-5V
4.7nF
C0G
1kΩ
0.1%
1kΩ
1kΩ
2.2nF ADC INPUT FILTER
4.7nF
C0G
499
0.1%
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX44206AUA+ -40°C to +125°C 8 µMAX-EP* +AACT
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 µMAX-EP U8E+2 21-0107 90-0145
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
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Ordering Information
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 11/14 Initial release
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2014 Maxim Integrated Products, Inc.
29
MAX44206 180MHz, Low-Noise, Low-Distortion, Fully
Differential Op Amp/ADC Driver
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.