FEATURES
TYPICAL APPLICATIONS CIRCUIT
APPLICATIONS
Portable and battery-powered instruments and systems
High channel density data acquisition systems
Precision analog-to-digital converter (ADC) drivers
Voltage reference buffers
Portable point of sales terminals
Active RFID readers
5V
C2
10µF
IN+
REF VDD
IN–
C1
2.7nF
AD7980
13391-001
ADA4806-1
R3
20Ω
GND
Figure 1. Driving the AD7980 with the ADA4806-1
Sleep mode reduces the amplifier quiescent current to 74 µA
and provides a fast turn-on time of only 0.45 µs, enabling the
use of dynamic power scaling for sample rates approaching
2 MSPS. For additional power savings at lower samples rates,
the shutdown mode further reduces the quiescent current to
only 2.9 µA.
The ADA4806-1 operates over a wide range of supply voltages
and is fully specified at supplies of 3 V, 5 V and ±5 V. This
amplifier is available in a compact, 8-lead SOT-23 package and
is rated to operate over the industrial temperature range of
−40°C to +125°C.
3.5
3.0
The ADA4806-1 is a high speed, voltage feedback, rail-to-rail
output, single operational amplifier with three power modes:
full power mode, sleep mode, and shutdown mode. In full
power mode, this amplifier provides a wide bandwidth of 105 MHz
at a gain of +1, a fast slew rate 160 V/μs, and excellent dc precision
with a low input offset voltage of 125 μV (maximum) and an input
offset voltage drift of 1.5 μV/°C (maximum), while con-suming
only 500 μA of quiescent current. Despite being a low power
amplifier, the ADA4806-1 provides excellent overall
performance, making it ideal for low power, high resolution
data conversion systems.
2.5
SHUTDOWN MODE
2.0
1.5
1.0
SLEEP MODE
0.5
0
1
10
100
ADC SAMPLE RATE (ksps)
1000
Figure 2. Quiescent Power Dissipation vs. ADC Sample Rate,
Using Dynamic Power Scaling for the Two Low Power Modes
Table 1. Complementary ADCs to the ADA4806-1
Product
AD7980
AD7982
AD7984
1
Rev. 0
VDD
C4
100nF
C3
0.1µF
5V
0V TO VREF
GENERAL DESCRIPTION
For data conversion applications where minimizing power
dissipation is paramount, the ADA4806-1 offers a method to
reduce power by dynamically scaling the quiescent power of the
ADC driver with the sampling rate of the system by switching the
amplifier to a lower power mode between samples.
ADA4806-1
2.5V REF
POWER CONSUMPTION (mW)
Ultralow supply current
Full power mode: 500 µA
Sleep mode: 74 µA
Shutdown mode: 2.9 µA
Dynamic power scaling
Turn-on time from shutdown mode: 1.5 µs
Turn-on time from sleep mode: 0.45 µs
High speed performance with dc precision
Input offset voltage: 125 µV maximum
Input offset voltage drift: 1.5 µV/°C maximum
−3 dB bandwidth: 105 MHz
Slew rate: 160 V/ µs
Low noise and distortion
5.9 nV/√Hz input voltage noise with 8 Hz 1/f corner
−102 dBc/−126 dBc HD2/HD3 at 100 kHz
Wide supply range: 2.7 V to 10 V
Small package: 8-lead SOT-23
13391-611
Data Sheet
0.2 µV/°C Offset Drift, 105 MHz, Low Power,
Multimode, Rail-to-Rail Amplifier
ADA4806-1
ADC Power (mW)
4.0
7.0
10.5
Throughput
(MSPS)
1
1
1.33
Resolution
(Bits)
16
18
18
SNR
(dB)
90.51
98
98.5
This SNR value is for the A Grade version of the AD7980.
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©2015 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
ADA4806-1
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Amplifier Description................................................................ 18
Applications ....................................................................................... 1
Input Protection ......................................................................... 18
General Description ......................................................................... 1
Shutdown/Sleep Mode Operation............................................ 18
Typical Applications Circuit............................................................ 1
Noise Considerations ................................................................. 19
Revision History ............................................................................... 2
Applications Information .............................................................. 20
Specifications..................................................................................... 3
Slew Enhancement ..................................................................... 20
±5 V Supply ................................................................................... 3
Effect of Feedback Resistor on Frequency Response ............ 20
5 V Supply...................................................................................... 4
Compensating Peaking in Large Signal Frequency Response... 20
3 V Supply...................................................................................... 6
Absolute Maximum Ratings............................................................ 8
Driving Low Power, High Resolution Successive
Approximation Register (SAR) ADCs..................................... 20
Thermal Resistance ...................................................................... 8
Dynamic Power Scaling............................................................. 21
Maximum Power Dissipation ..................................................... 8
Single-Ended to Differential Conversion ................................... 23
ESD Caution .................................................................................. 8
Layout Considerations ............................................................... 23
Pin Configurations and Function Descriptions ........................... 9
Outline Dimensions ....................................................................... 24
Typical Performance Characteristics ........................................... 10
Ordering Guide .......................................................................... 24
Test Circuits ..................................................................................... 17
Theory of Operation ...................................................................... 18
REVISION HISTORY
9/15—Revision 0: Initial Version
Rev. 0 | Page 2 of 24
Data Sheet
ADA4806-1
SPECIFICATIONS
±5 V SUPPLY
VS = ±5 V at TA = 25°C; RF = 0 Ω for G = +1; otherwise, RF = 1 kΩ; RL = 2 kΩ to ground; unless otherwise noted.
Table 2.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Bandwidth for 0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion, HD2/HD3 1
Input Voltage Noise
Input Voltage Noise 1/f Corner Frequency
0.1 Hz to 10 Hz Voltage Noise
Input Current Noise
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift 2
Input Bias Current (IB)
Input Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Common Mode
Differential Mode
Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio (CMRR)
SHUTDOWN PIN
SHUTDOWN Voltage
Low
High
SHUTDOWN Current
Low
High
Turn-Off Time
Turn-On Time
Test Conditions/Comments
Min
Typ
Max
Unit
G = +1, VOUT = 0.02 V p-p
G = +1, VOUT = 2 V p-p
G = +1, VOUT = 0.02 V p-p
G = +1, VOUT = 2 V step
G = +2, VOUT = 4 V step
G = +1, VOUT = 2 V step
G = +2, VOUT = 4 V step
120
40
18
190
250
35
78
MHz
MHz
MHz
V/µs
V/µs
ns
ns
fC = 20 kHz, VOUT = 2 V p-p
fC = 100 kHz, VOUT = 2 V p-p
fC = 20 kHz, VOUT = 4 V p-p, G = +1
fC = 100 kHz, VOUT = 4 V p-p, G = +1
fC = 20 kHz, VOUT = 4 V p-p, G = +2
fC = 100 kHz, VOUT = 4 V p-p, G = +2
f = 100 kHz
−114/−140
−102/−128
−109/−143
−93/−130
−113/−142
−96/−130
5.2
8
44
0.7
dBc
dBc
dBc
dBc
dBc
dBc
nV/√Hz
Hz
nV rms
pA/√Hz
f = 100 kHz
Full power mode
Low power mode, SLEEP = −VS
TMIN to TMAX, 4 σ
Full power mode
Low power mode, SLEEP = −VS
VOUT = −4.0 V to +4.0 V
107
13
800
0.2
550
3
2.1
111
125
1.5
800
25
50
260
1
VIN, CM = −4.0 V to +4.0 V
−5.1
103
Powered down
Enabled
Powered down
Enabled
50% of SHUTDOWN to <10% of enabled
quiescent current
50% of SHUTDOWN to >99% of final VOUT
Rev. 0 | Page 3 of 24
−1.0
µV
µV
µV/°C
nA
nA
nA
dB
130
MΩ
kΩ
pF
V
dB
<−1.3
>−0.9
V
V
+4
+0.2
0.02
1.25
1.0
2.75
µA
µA
µs
1
3
µs
ADA4806-1
Parameter
SLEEP PIN
SLEEP Voltage
Low
High
SLEEP Current
Low
High
Turn-Off Time (Full Power Mode to Sleep Mode)
Turn-On Time (Sleep Mode to Full Power Mode)
OUTPUT CHARACTERISTICS
Output Overdrive Recovery Time
(Rising/Falling Edge)
Output Voltage Swing
Short-Circuit Current
Linear Output Current
Off Isolation
Capacitive Load Drive
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Power Supply Rejection Ratio (PSRR)
Positive
Negative
1
2
Data Sheet
Test Conditions/Comments
Min
Powered down
Enabled
Low Power Mode, SLEEP = −VS
Enabled
50% of SLEEP to 30% of enabled quiescent
current
50% of SLEEP to >99% of final VOUT
−1.0
V
V
1.0
240
µA
µA
ns
450
600
ns
95/100
−4.98
Full power mode
Low power mode, SLEEP = −VS
SHUTDOWN = −VS
ns
85/73
1.4/1.8
±58
+4.98
V
mA
mA
mA
41
15
dB
pF
570
85
7.4
100
100
Unit
+0.2
0.02
180
2.7
+VS = +3 V to +5 V, −VS = −5 V
+VS = +5 V, −VS = −3 V to −5 V
Max
<−1.3
>−0.9
VIN = +6 V to −6 V, G = +2
RL = 2 kΩ
Sourcing/sinking; full power mode
Sourcing/sinking; low power mode, SLEEP = −VS
<1% total harmonic distortion (THD) at 100 kHz,
VOUT = 2 V p-p
VIN = 0.5 V p-p, f = 1 MHz, SHUTDOWN = −VS
30% overshoot
Typ
10
625
12
119
122
V
µA
µA
µA
dB
dB
fC is the fundamental frequency.
Guaranteed, but not tested.
5 V SUPPLY
VS = 5 V at TA = 25°C; RF = 0 Ω for G = +1; otherwise, RF = 1 kΩ; RL = 2 kΩ to midsupply; unless otherwise noted.
Table 3.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Bandwidth for 0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
Test Conditions/Comments
G = +1, VOUT = 0.02 V p-p
G = +1, VOUT = 2 V p-p
G = +1, VOUT = 0.02 V p-p
G = +1, VOUT = 2 V step
G = +2, VOUT = 4 V step
G = +1, VOUT = 2 V step
G = +2, VOUT = 4 V step
Rev. 0 | Page 4 of 24
Min
Typ
105
35
20
160
220
35
82
Max
Unit
MHz
MHz
MHz
V/µs
V/µs
ns
ns
Data Sheet
Parameter
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion, HD2/HD3 1
Input Voltage Noise
Input Voltage Noise 1/f Corner
0.1 Hz to 10 Hz Voltage Noise
Input Current Noise
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift 2
Input Bias Current
Input Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Common Mode
Differential Mode
Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
SHUTDOWN PIN
SHUTDOWN Voltage
Low
High
SHUTDOWN Current
Low
High
Turn-Off Time
Turn-On Time
SLEEP PIN
SLEEP Voltage
Low
High
SLEEP Current
Low
High
Turn-Off Time (Full Power Mode to
Sleep Mode)
Turn-On Time (Sleep Mode to Full
Power Mode)
ADA4806-1
Test Conditions/Comments
Min
fC = 20 kHz, VOUT = 2 V p-p
fC = 100 kHz, VOUT = 2 V p-p
fC = 20 kHz, G = +2, VOUT = 4 V p-p
fC = 100 kHz, G = +2, VOUT = 4 V p-p
f = 100 kHz
Max
−114/−135
−102/−126
−107/−143
−90/−130
5.9
8
54
0.6
f = 100 kHz
Full power mode
Low power mode, SLEEP = −VS
TMIN to TMAX, 4 σ
Full power mode
Low power mode, SLEEP = −VS
VOUT = 1.25 V to 3.75 V
Typ
105
10
500
0.2
470
3
0.4
109
dBc
dBc
dBc
dBc
nV/√Hz
Hz
nV rms
pA/√Hz
125
1.5
720
50
260
1
VIN, CM = 1.25 V to 3.75 V
−0.1
103
Powered down
Enabled
Powered down
Enabled
50% of SHUTDOWN to <10% of enabled
quiescent current
50% of SHUTDOWN to >99% of final VOUT
−1.0
Powered down
Enabled
Low power mode, SLEEP = −VS
Enabled
50% of SLEEP to 30% of enabled quiescent
current
50% of SLEEP to >99% of final VOUT
Rev. 0 | Page 5 of 24
µV
µV
µV/°C
nA
nA
nA
dB
133
MΩ
kΩ
pF
V
dB
<1.5
>1.9
V
V
+4
+0.1
0.01
0.9
1.0
1.25
µA
µA
µs
1.5
4
µs
<1.5
>1.9
−1.0
Unit
V
V
+0.1
0.01
150
1.0
185
µA
µA
ns
450
600
ns
ADA4806-1
Parameter
OUTPUT CHARACTERISTICS
Overdrive Recovery Time (Rising/Falling
Edge)
Output Voltage Swing
Short-Circuit Current
Linear Output Current
Off Isolation
Capacitive Load Drive
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Power Supply Rejection Ratio
Positive
Negative
1
2
Data Sheet
Test Conditions/Comments
Min
VIN = −1 V to +6 V, G = +2
RL = 2 kΩ
Sourcing/sinking; full power mode
Sourcing/sinking; low power mode, SLEEP = −VS
<1% THD at 100 kHz, VOUT = 2 V p-p
VIN = 0.5 V p-p, f = 1 MHz, SHUTDOWN = −VS
30% overshoot
Typ
130/145
0.02
2.7
500
74
2.9
100
100
Unit
ns
4.98
V
mA
mA
mA
dB
pF
10
520
V
µA
µA
µA
73/63
1.0/1.3
±47
41
15
Full power mode
Low power mode, SLEEP = −VS
SHUTDOWN = −VS
+VS = 1.5 V to 3.5 V, −VS = −2.5 V
+VS = 2.5 V, −VS = −1.5 V to −3.5 V
Max
4
120
126
dB
dB
fC is the fundamental frequency.
Guaranteed, but not tested.
3 V SUPPLY
VS = 3 V at TA = 25°C; RF = 0 Ω for G = +1; otherwise, RF = 1 kΩ; RL = 2 kΩ to midsupply; unless otherwise noted.
Table 4.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Bandwidth for 0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion, HD2/HD3 1
Input Voltage Noise
Input Voltage Noise 1/f Corner
0.1 Hz to 10 Hz Voltage Noise
Input Current Noise
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift 2
Input Bias Current
Input Offset Current
Open-Loop Gain
Test Conditions/Comments
Min
Typ
Max
Unit
G = +1, VOUT = 0.02 V p-p
G = +1, VOUT = 1 V p-p, +VS = 2 V, −VS = −1 V
G = +1, VOUT = 0.02 V p-p
G = +1, VOUT = 1 V step, +VS = 2 V, −VS = −1 V
G = +1, VOUT = 1 V step
95
30
35
85
41
MHz
MHz
MHz
V/µs
ns
fC = 20 kHz, VOUT = 1 V p-p, +VS = 2 V, −VS = −1 V
fC = 100 kHz, VOUT = 1 V p-p, +VS = 2 V, −VS = −1 V
f = 100 kHz
−123/−143
−107/−133
6.3
8
55
0.8
dBc
dBc
nV/√Hz
Hz
nV rms
pA/√Hz
f = 100 kHz
Full power mode
Low power mode, SLEEP = −VS
TMIN to TMAX, 4 σ
Full power mode
Low power mode, SLEEP = −VS
VOUT = 1.1 V to 1.9 V
Rev. 0 | Page 6 of 24
100
7
300
0.2
440
3
0.5
107
125
1.5
690
µV
µV
µV/°C
nA
nA
nA
dB
Data Sheet
Parameter
INPUT CHARACTERISTICS
Input Resistance
Common Mode
Differential Mode
Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
SHUTDOWN PIN
SHUTDOWN Voltage
Low
High
SHUTDOWN Current
Low
High
Turn-Off Time
Turn-On Time
SLEEP PIN
SLEEP Voltage
Low
High
SLEEP Current
Low
High
Turn-Off Time (Full Power Mode to Sleep Mode)
Turn-On Time (Sleep Mode to Full Power Mode)
OUTPUT CHARACTERISTICS
Output Overdrive Recovery Time
(Rising/Falling Edge)
Output Voltage Swing
Short-Circuit Current
Linear Output Current
Off Isolation
Capacitive Load Drive
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Power Supply Rejection Ratio
Positive
Negative
1
2
ADA4806-1
Test Conditions/Comments
Min
Typ
Max
50
260
1
VIN, CM = 0.5 V to 2 V
−0.1
89
Powered down
Enabled
Powered down
Enabled
50% of SHUTDOWN to <10% of enabled
quiescent current
50% of SHUTDOWN to >99% of final VOUT
−1.0
Powered down
Enabled
Low Power Mode, SLEEP = −VS
Enabled
50% of SLEEP to 30% of enabled quiescent current
50% of SLEEP to >99% of final VOUT
VIN = −1 V to +4 V, G = +2
RL = 2 kΩ
Sourcing/sinking; full power mode
Sourcing/sinking; low power mode, SLEEP = −VS
<1% THD at 100 kHz, VOUT = 1 V p-p
VIN = 0.5 V p-p, f = 1 MHz, SHUTDOWN = −VS
30% overshoot
117
MΩ
kΩ
pF
V
dB
<0.7
>1.1
V
V
+2
+0.1
0.01
0.9
1.0
1.25
µA
µA
µs
2.5
8
µs
<0.7
>1.1
−1.0
+0.1
0.01
155
450
0.02
fC is the fundamental frequency.
Guaranteed, but not tested.
Rev. 0 | Page 7 of 24
1.0
210
600
470
70
1.3
96
96
119
125
µA
µA
ns
ns
ns
2.98
V
mA
mA
mA
dB
pF
10
495
V
µA
µA
µA
65/47
1.0/1.3
±40
41
15
2.7
+VS = 1.5 V to 3.5 V, −VS = −1.5 V
+VS = 1.5 V, −VS = −1.5 V to −3.5 V
V
V
135/175
Full power mode
Low power mode, SLEEP = −VS
SHUTDOWN = −VS
Unit
3
dB
dB
ADA4806-1
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 5.
Parameter
Supply Voltage
Power Dissipation
Common-Mode Input Voltage
Differential Input Voltage
Storage Temperature Range
Operating Temperature Range
Lead Temperature (Soldering, 10 sec)
Junction Temperature
Rating
11 V
See Figure 3
−VS − 0.7 V to +VS + 0.7 V
±1 V
−65°C to +125°C
−40°C to +125°C
300°C
150°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
THERMAL RESISTANCE
θJA is specified for the worst case conditions, that is, θJA is specified
for a device soldered in a circuit board for surface-mount packages.
Table 6 lists the θJA for the ADA4806-1.
The quiescent power dissipation is the voltage between the supply
pins (VS) multiplied by the quiescent current (IS).
PD = Quiescent Power + (Total Drive Power − Load Power)
V
V
PD = (VS × I S ) +  S × OUT
RL
 2
RMS output voltages must be considered. If RL is referenced
to −VS, as in single-supply operation, the total drive power is
VS × IOUT. If the rms signal levels are indeterminate, consider the
worst case, when VOUT = VS/4 for RL to midsupply.
PD = (VS × I S ) +
(VS / 4)2
RL
In single-supply operation with RL referenced to −VS, the worst
case is VOUT = VS/2.
Airflow increases heat dissipation, effectively reducing θJA.
Additionally, more metal directly in contact with the package
leads and exposed pad from metal traces, through holes,
ground, and power planes reduces θJA.
Figure 3 shows the maximum safe power dissipation in the
package vs. the ambient temperature on a JEDEC standard,
4-layer board. θJA values are approximations.
Table 6. Thermal Resistance
1.0
Unit
°C/W
TJ = 150°C
0.9
MAXIMUM POWER DISSIPATION
The maximum safe power dissipation for the ADA4806-1 is
limited by the associated rise in junction temperature (TJ) on
the die. At approximately 150°C, which is the glass transition
temperature, the properties of the plastic change. Even temporarily
exceeding this temperature limit may change the stresses that the
package exerts on the die, permanently shifting the parametric
performance of the ADA4806-1. Exceeding a junction temperature
of 175°C for an extended period of time can result in changes in
silicon devices, potentially causing degradation or loss of
functionality.
The power dissipated in the package (PD) is the sum of the
quiescent power dissipation and the power dissipated in the die
due to the ADA4806-1 output load drive.
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
–50
–30
–10
10
30
50
70
90
AMBIENT TEMPERATURE (°C)
110
130
13391-600
θJA
209.1
MAXIMUM POWER DISSIPATION (W)
Package Type
8-Lead SOT-23
 VOUT 2
−

RL

Figure 3. Maximum Power Dissipation vs. Ambient Temperature for a
4-Layer Board
ESD CAUTION
Rev. 0 | Page 8 of 24
Data Sheet
ADA4806-1
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VOUT 1
8
+VS
NC 2
7
SHUTDOWN
–VS 3
6
SLEEP
+IN 4
5
–IN
13391-002
ADA4806-1
NOTES
1. NC = NO CONNECTION. DO NOT CONNECT TO THIS PIN.
Figure 4. Pin Configuration
Table 7. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
Mnemonic
VOUT
NC
−VS
+IN
−IN
SLEEP
SHUTDOWN
+VS
Description
Output.
No Connection. Do not connect to this pin.
Negative Supply.
Noninverting Input.
Inverting Input.
Low Power Mode.
Power-Down Mode.
Positive Supply.
Rev. 0 | Page 9 of 24
ADA4806-1
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
RL = 2 kΩ, unless otherwise noted. When G = +1, RF = 0 Ω.
3
G = +2
NORMALIZED CLOSED-LOOP GAIN (dB)
0
G = +1
G = +10
–3
G = +5
–6
G = +2
–9
VS = ±2.5V
VOUT = 20mV p-p
RL = 2kΩ
RF = 1kΩ
–12
0.1
1
10
1000
100
FREQUENCY (MHz)
0
G = +5
–3
–6
–9
G = +10
VS = ±2.5V
VOUT = 2V p-p
RF = 1kΩ
RL = 2kΩ
–12
0.1
13391-206
NORMALIZED CLOSED-LOOP GAIN (dB)
G = +1
1
100
10
FREQUENCY (MHz)
Figure 5. Small Signal Frequency Response for Various Gains
Figure 8. Large Signal Frequency Response for Various Gains
3
3
13391-015
3
–40°C
–40°C
+25°C
CLOSED-LOOP GAIN (dB)
+25°C
–3
+125°C
–6
–12
0.1
+125°C
–3
–6
VS = ±2.5V
G = +1
VOUT = 2V p-p
RL = 2kΩ
VS = ±2.5V
G = +1
VOUT = 20mV p-p
RL = 2kΩ
1
0
10
100
1000
FREQUENCY (MHz)
–9
0.1
Figure 6. Small Signal Frequency Response for Various Temperatures
1
10
100
FREQUENCY (MHz)
13391-016
–9
13391-208
CLOSED-LOOP GAIN (dB)
0
Figure 9. Large Signal Frequency Response for Various Temperatures
3
3
VS = ±5V
VOUT = 0.5V p-p
VS = ±2.5V
VOUT = 20mV p-p
CLOSED-LOOP GAIN (dB)
CLOSED-LOOP GAIN (dB)
0
VS = ±1.5V
–3
–6
0
VOUT = 2V p-p
–3
–9
10
FREQUENCY (MHz)
100
1000
Figure 7. Small Signal Frequency Response for Various Supply Voltages
Rev. 0 | Page 10 of 24
–6
0.1
1
10
100
1000
FREQUENCY (MHz)
Figure 10. Frequency Response for Various Output Voltages
13391-211
1
13391-207
–12
0.1
VOUT = 100mV p-p
VS = ±2.5V
G = +1
RL = 2kΩ
G = +1
VOUT = 20mV p-p
RL = 2kΩ
Data Sheet
ADA4806-1
0.6
12
VS = ±2.5V
G = +1
RL = 2kΩ
VOUT = 20mV p-p
0.4
CL = 10pF
6
CL = 5pF
3
CL = 0pF
0
CL = 15pF
RS = 226Ω
–3
VS = ±2.5V
G = +1
RL = 2kΩ
VOUT = 20mV p-p
0.5
CLOSED-LOOP GAIN (dB)
CLOSED-LOOP GAIN (dB)
9
CL = 15pF
–6
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–9
10
–0.6
13391-309
1
100
FREQUENCY (MHz)
1
10
Figure 11. Small Signal Frequency Response for Various Capacitive Loads
(See Figure 47)
Figure 14. Small Signal 0.1 dB Bandwidth
–50
–50
–60
–70
HD2, G = +1
HD2 VS = ±5V
–80
DISTORTION (dBc)
HD2, G = +2
–90
–100
–110
–120
HD3, G = +2
–130
–90
–100
–110
HD2 VS = +2V/–1V
–120
HD2 VS = ±2.5V
–130
–140
–140
–150
–150
HD3 VS = +2V/–1V
HD3 VS = ±2.5V
HD3 VS = ±5V
HD3, G = +1
10
100
1000
–160
FREQUENCY (kHz)
Figure 12. Distortion vs. Frequency for Various Gains
TOTAL HARMONIC DISTORTION (dB)
–50
–60
VS = ±2.5V
VIN, CM = 0V
G = +1
RL = 2kΩ
–70
–50
INPUT COMMON-MODE
VOLTAGE UPPER LIMIT
(+VS – 1V)
1000
HD2 VS = ±5V
–70
HD2 VS = ±2.5V
–80
–80
–90
VIN = 100kHz
–110
–90
–100
HD2 VS = +2V/–1V
–110
–120
–130
–120
VIN = 10kHz
HD3 VS = +2V/–1V
–140
–130
HD3 VS = ±2.5V
–150
0.50
0.75
1.00
1.25
1.50
OUTPUT VOLTAGE (V peak)
1.75
2.00
13391-316
–140
0.25
100
FREQUENCY (kHz)
VS = ±5V, VOUT = 4V p-p
VS = ±2.5V, VOUT = 4V p-p
VS = +2V/–1V, VOUT = 1V p-p
–60
VIN = 1MHz
–100
10
Figure 15. Distortion vs. Frequency for Various Supplies, G = +1
DISTORTION (dBc)
–40
1
Figure 13. Total Harmonic Distortion vs. Output Voltage For Various
Frequencies
Rev. 0 | Page 11 of 24
–160
HD3 VS = ±5V
1
10
100
FREQUENCY (kHz)
Figure 16. Distortion vs. Frequency, G = +2
1000
13391-518
1
13391-514
–160
13391-517
–80
DISTORTION (dBc)
VS = ±5V, VOUT = 2V p-p
VS = ±2.5V, VOUT = 2V p-p
VS = +2V/–1V, VOUT = 1V p-p
VS = ±5V, VOUT = 4V p-p
–60
–70
100
FREQUENCY (MHz)
13391-110
–0.5
–12
ADA4806-1
Data Sheet
90
12
VS = ±2.5V
G = +1
80
VS = ±2.5V
G = +1
CURRENT NOISE (pA/√Hz)
VOLTAGE NOISE (nV/√Hz)
10
70
60
50
40
30
20
8
6
4
2
10
1
1k
100
10k
1M
100k
10M
100M
FREQUENCY (Hz)
0
13391-219
0
0.1
1
10
10k
1k
100k
1M
10M
FREQUENCY (Hz)
Figure 17. Voltage Noise vs. Frequency
Figure 20. Current Noise vs. Frequency (See Figure 48)
300
–10
VS = ±2.5V
250 AVERAGE NOISE = 54nV rms
VS = ±2.5V
G = +1
RL = 2kΩ
VIN = 0.5 Vp-p
SHUTDOWN = –VS
SLEEP = –VS
–20
200
150
–30
100
ISOLATION (dB)
AMPLITUDE (nV)
100
13391-018
10
50
0
–50
–100
–40
–50
–60
–150
–70
–200
–80
0
1
2
3
4
5
6
7
8
9
10
TIME (Seconds)
–90
0.01
13391-318
–300
100
0.3
VS = +5V
G = +1
VOUT = 2V STEP
RL = 2kΩ
VS = ±2.5V
ΔVS, ΔVCM = 100mV p-p
0.2
–20
–PSRR
–40
–60
CMRR
–80
0.1
0
–0.1
+PSRR
–100
–0.2
–140
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
–0.3
0
20
40
60
80
100
120
140
TIME (ns)
Figure 22. Settling Time to 0.1%
Figure 19. CMRR, PSRR vs. Frequency
Rev. 0 | Page 12 of 24
160
180
13391-030
–120
13391-232
CMRR, PSRR (dB)
10
Figure 21. Forward Isolation vs. Frequency
SETTLING (%)
0
1
FREQUENCY (MHz)
Figure 18. 0.1 Hz to 10 Hz Voltage Noise
20
0.1
13391-601
–250
Data Sheet
ADA4806-1
35
4500
VS = ±2.5V
= 9.8µV
σ = 19.5µV
4000
VS = ±2.5V
T = –40°C TO +125°C
= –0.19µV/°C
σ = 0.28µV/°C
30
3500
NUMBER OF UNITS
25
UNITS (%)
3000
2500
2000
20
15
1500
10
1000
5
60
30
–30
0
–60
INPUT OFFSET VOLTAGE (µV)
–90
90
120
0
13391-613
0
–120
–1.6
1.2
0.8
1.6
Figure 26. Input Offset Voltage Drift Distribution
100
150
VS = ±2.5V
10 UNITS
VS = ±2.5V
30 UNITS
100
60
INPUT OFFSET VOLTAGE (µV)
INPUT OFFSET VOLTAGE (µV)
0.4
0
–0.4
INPUT OFFSET VOLTAGE DRIFT (µV/°C)
Figure 23. Input Offset Voltage Distribution
80
–0.8
–1.2
13391-323
500
40
20
0
–20
–40
–60
50
0
–50
–100
–2.5
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0
1.5
2.0
INPUT COMMON-MODE VOLTAGE (V)
–150
–40
13391-327
–25
20
35
50
65
80
95
110
6
–400
630
VS = ±5V
610
125
Figure 27. Input Offset Voltage vs. Temperature
650
IB–
–450
4
590
INPUT BIAS CURRENT (nA)
570
550
530
510
VS = ±2.5V
490
470
450
–500
IB+
2
–550
INPUT OFFSET CURRENT
0
–600
–650
–2
–700
VS = ±1.5V
430
–4
–750
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
13391-257
410
–800
–0.4
–6
0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
3.6
4.0
INPUT COMMON-MODE VOLTAGE (V)
Figure 28. Input Bias Current and Input Offset Current vs.
Input Common-Mode Voltage
Figure 25. Input Bias Current vs. Temperature for Various Supplies
(See Figure 49)
Rev. 0 | Page 13 of 24
13391-135
INPUT BIAS CURRENT (nA)
5
TEMPERATURE (°C)
Figure 24. Input Offset Voltage vs. Input Common-Mode Voltage
390
–40
–10
INPUT OFFSET CURRENT (nA)
–100
–3.0
13391-013
–80
ADA4806-1
Data Sheet
15
1.5
G = +1
VOUT = 20mV p-p
VS = ±5V, VIN, CM = 0V, VOUT = 2V p-p
G = +1
VS = ±2.5V, VIN, CM = 0V, VOUT = 2V p-p
10
1.0
OUTPUT VOLTAGE (V)
5
0
–5
VS = ±1.5V
–10
0.5
0
–0.5
–1.0
50
100
150
200
250
300
TIME (ns)
13391-024
0
–1.5
0
VOUT
0
–1
–2
–3
300
350
VS = ±2.5V
G = +2
3
2
VOUT
1
0
–1
–2
–3
–4
0
100
200
300
400 500 600
TIME (ns)
700
800
900
1000
13391-128
–4
250
2×VIN
4
2
1
200
5
INPUT AND OUTPUT VOLTAGE (V)
INPUT AND OUTPUT VOLTAGE (V)
3
150
Figure 32. Large Signal Transient Response for Various Supplies
VS = ±2.5V
G = +1
VIN
100
TIME (ns)
Figure 29. Small Signal Transient Response for Various Supplies
4
50
13391-025
VS = ±1.5V, VIN, CM = –0.5V, VOUT = 1V p-p
VS = ±5V
–15
–5
0
100
200
300
400 500 600
TIME (ns)
700
800
900
1000
13391-129
OUTPUT VOLTAGE (mV)
VS = ±2.5V
Figure 33. Output Overdrive Recovery Time
Figure 30. Input Overdrive Recovery Time
0.8
0.8
0.7
0.7
+125°C
0.6
OUTPUT VOLTAGE (V)
0.5
+25°C
0.4
–40°C
0.3
0.2
–0.1
–0.5
0
0.5
1.0
TIME (µs)
1.5
0.4
+25°C
0.3
–40°C
0.2
0.1
VS = ±2.5V
G = +1
RL = 2kΩ
0
+125°C
0.5
VS = ±2.5V
G = +1
RL = 2kΩ
0
2.0
–0.1
–0.25
Figure 31. Turn-On Response Time from Shutdown for Various Temperatures
(See Figure 50)
0
0.25
TIME (µs)
0.50
0.75
13391-605
0.1
13391-602
OUTPUT VOLTAGE (V)
0.6
Figure 34. Turn-On Response Time from Sleep for Various Temperatures
(See Figure 50)
Rev. 0 | Page 14 of 24
Data Sheet
ADA4806-1
800
800
700
+125°C
+125°C
700
G = +1
RL = 2kΩ
600
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
VS = ±2.5V
VS = ±2.5V
G = +1
RL = 2kΩ
500
+25°C
400
300
–40°C
200
100
600
500
400
300
+25°C
200
100
1
0
2
3
4
5
6
TIME (µs)
0
–1
13391-258
–1
Figure 35. Turn-Off Response Time to Shutdown for Various Temperatures
(See Figure 51)
4
5
6
0.7
VS = ±5V
VS = ±5V
0.6
OUTPUT VOLTAGE (V)
0.6
0.5
0.4
VS = +2/–1V
0.3
0.2
VS = ±2.5V
VS = ±2.5V
0.5
0.4
0.3
VS = +2V/–1V
0.2
0.1
0
0
1
TIME (µs)
2
3
–0.1
–0.25
13391-603
–0.1
–1
G = +1
RL = 2kΩ
0
G = +1
RL = 2kΩ
0
0.25
0.5
0.75
TIME (µs)
Figure 36. Turn-On Response Time from Shutdown for Various Supplies
13391-608
0.1
Figure 39. Turn-On Response Time from Sleep for Various Supplies
800
800
G = +1
RL = 2kΩ
700
700
VS = ±5V
SUPPLY CURRENT (µA)
600
VS = ±2.5V
500
400
VS = ±1.5V
300
200
100
G = +1
RL = 2kΩ
VS = ±5V
600
VS = ±2.5V
500
400
VS = ±1.5V
300
200
–1
0
1
2
3
TIME (µs)
4
5
6
13391-242
100
0
–1
Figure 37. Turn-Off Response Time to Shutdown for Various Supplies
Rev. 0 | Page 15 of 24
0
1
2
3
TIME (µs)
4
5
6
Figure 40. Turn-Off Response Time to Sleep for Various Supplies
13391-609
OUTPUT VOLTAGE (V)
2
3
TIME (µs)
0.8
0.7
SUPPLY CURRENT (µA)
1
Figure 38. Turn-Off Response Time to Sleep for Various Temperatures
(See Figure 51)
0.8
0
0
13391-607
–40°C
0
Data Sheet
800
140
750
130
QUIESCENT SUPPLY CURRENT (µA)
700
650
600
VS = ±5V
550
500
VS = ±1.5V
450
VS = ±2.5V
400
120
110
100
80
70
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
40
–40
13391-256
–25
Figure 41. Quiescent Supply Current vs. Temperature
3.5
3.5
OUTPUT CURRENT (mA)
4.0
–40°C
2.5
+125°C
+25°C
2.0
–10
5
20
35
50
65
TEMPERATURE (°C)
80
95
1.5
1.0
VS = ±5.0V
VS = ±2.5V
3.0
2.5
VS = ±1.5V
2.0
1.5
1.0
Figure 42. SHUTDOWN and SLEEP Threshold vs. Supply Voltage from Ground
for Various Temperatures
2
5
65
20
35
50
TEMPERATURE (°C)
80
95
120
25.0
–20
100
–1
23.5
–2
23.0
–3
22.5
–4
200
400
600
800
1000
1200
TIME (Hours)
1400
OPEN-LOOP GAIN (dB)
24.0
–40
80
–60
60
–80
–100
PHASE
40
–120
20
–140
22.0
0
21.5
–20
10
13391-542
0
TEMPERATURE (°C)
24.5
OIL BATH
TEMPERATURE
125
0
GAIN
1
110
Figure 45. Sleep Mode Output Current vs. Temperature
25.5
VS = ±2.5V
6 UNITS, SOLDERED TO PCB
–10
Figure 43. Long-Term VOS Drift
–160
100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 46. Open-Loop Gain and Phase Margin
Rev. 0 | Page 16 of 24
OPEN-LOOP PHASE (Degrees)
3
–25
13391-604
0
–40
13391-236
SUPPLY VOLTAGE FROM GROUND (V)
0
125
0.5
0.5
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
–5
110
Figure 44. Sleep Mode Quiescent Supply Current vs. Temperature
4.0
3.0
–25
13391-606
50
300
–40
SHUTDOWN AND SLEEP THRESHOLD (V)
VS = ±1.5V
60
350
CHANGE IN INPUT OFFSET VOLTAGE (µV)
VS = ±2.5V
VS = ±5.0V
90
–180
100M
13391-026
QUIESCENT SUPPLY CURRENT (µA)
ADA4806-1
Data Sheet
ADA4806-1
TEST CIRCUITS
SHUTDOWN OR SLEEP
+2.5V
VOUT
+2.5V
–2.5V
50Ω
VOUT
CL
2kΩ
0.5V
2kΩ
–2.5V
+
5V
–
13391-404
VIN
20mV p-p
13391-401
RS
–2.5V
Figure 47. Output Capacitive Load Behavior Test Circuit (See Figure 11)
Figure 50. Turn-On Response Test Circuit (See Figure 31 and Figure 34)
+2.5V
IS SHUTDOWN OR SLEEP
+2.5V
VOUT
VOUT
2kΩ
–2.5V
+
5V
–
–2.5V
Figure 48. Current Noise Test Circuit (See Figure 20)
Figure 51. Turn-Off Response Test Circuit (See Figure 35 and Figure 38)
13391-403
IB+
IB –
13391-405
–2.5V
13391-402
75kΩ
Figure 49. Input Bias Current Temperature Test Circuit (See Figure 25)
Rev. 0 | Page 17 of 24
ADA4806-1
Data Sheet
THEORY OF OPERATION
AMPLIFIER DESCRIPTION
The ADA4806-1 has a bandwidth of 105 MHz and a slew rate of
160 V/µs. It has an input referred voltage noise of only 5.9 nV/√Hz.
The ADA4806-1 operates over a supply voltage range of 2.7 V to
10 V and consumes only 500 µA of supply current at VS = 5 V. The
low end of the supply range allows −10% variation of a 3 V supply.
The amplifier is unity-gain stable, and the input structure results in
an extremely low input 1/f noise. The ADA4806-1 uses a slew
enhancement architecture, as shown in Figure 52. The slew
enhancement circuit detects the absolute difference between the
two inputs. It then modulates the tail current, ITAIL, of the input
stage to boost the slew rate. The architecture allows a higher
slew rate and fast settling time with low quiescent current while
maintaining low noise.
SLEW ENHANCEMENT CIRCUIT
+VS
ITAIL
TO DETECT
ABSOLUTE
VALUE
VIN+
VIN–
+IN
13391-255
–IN
INPUT
STAGE
Figure 52. Slew Enhancement Circuit
INPUT PROTECTION
The ADA4806-1 is fully protected from ESD events,
withstanding human body model ESD events of ±3.5 kV and
charged device model events of ±1.25 kV with no measured
performance degradation. The precision input is protected with
an ESD network between the power supplies and diode clamps
across the input device pair, as shown in Figure 53.
For differential voltages above approximately 1.2 V at room
temperature, and 0.8 V at 125°C, the diode clamps begin to
conduct. If large differential voltages must be sustained across
the input terminals, the current through the input clamps must
be limited to less than 10 mA. Series input resistors that are sized
appropriately for the expected differential overvoltage provide
the needed protection.
The ESD clamps begin to conduct for input voltages that are
more than 0.7 V above the positive supply and input voltages
more than 0.7 V below the negative supply. If an overvoltage
condition is expected, the input current must be limited to less
than 10 mA.
SHUTDOWN/SLEEP MODE OPERATION
Figure 54 shows the ADA4806-1 shutdown circuitry. To
maintain very low supply current in shutdown mode, no internal
pull-up resistor is supplied; therefore, the SHUTDOWN pin must
be driven high or low externally and must not be left floating.
Pulling the SHUTDOWN pin to ≥1 V below midsupply turns the
device off, reducing the supply current to 2.9 µA for a 5 V supply.
When the amplifier is powered down, its output enters a high
impedance state. The output impedance decreases as frequency
increases. In shutdown mode, a forward isolation of −62 dB can
be achieved at 100 kHz (see Figure 21).
A second circuit similar to Figure 54 is used for sleep mode
operation. Pulling the SLEEP pin low places the amplifier in a low
power state, drawing only 74 µA from a 5 V supply. Leaving the
amplifier biased on at a very low level greatly reduces the turnon time from sleep to full power mode, thus enabling dynamic
power scaling of the ADA4806-1 at higher sample rates.
The ADA4806-1 is not characterized for operation in sleep mode.
+VS
2.2R
1.1V
ESD
+VS
SHUTDOWN
BIAS
ESD
–IN
+IN
ESD
1.8R
ESD
TO ENABLE
AMPLIFIER
–VS
ESD
13391-006
ESD
Figure 54. Shutdown/Sleep Equivalent Circuit
TO THE REST OF THE AMPLIFIER
13391-005
–VS
Figure 53. Input Stage and Protection Diodes
The SHUTDOWN pin and the SLEEP pin are protected by ESD
clamps, as shown in Figure 54. Voltages beyond the power supplies
cause these diodes to conduct. To protect the SHUTDOWN and
SLEEP pins, ensure that the voltage to these pins does not
exceed 0.7 V above the positive supply or 0.7 V below the
negative supply. If an overvoltage condition is expected, the
input current must be limited to less than 10 mA with a series
resistor.
Rev. 0 | Page 18 of 24
Data Sheet
ADA4806-1
The output noise spectral density is calculated by
Table 8 summarizes the threshold voltages for the
SHUTDOWN and SLEEP pins for various supplies. Table 9
shows the truth table for the SHUTDOWN and SLEEP pins.
v n _ OUT =
2

R
R 
4kTR F + 1 + F  4kTRs + in+ 2 RS 2 + v n 2 +  F
R
G 

 RG
Table 8. Threshold Voltages for Enabled Mode and
Shutdown/Sleep Modes
+3 V
>+1.1 V
<+0.7 V
+5 V
>+1.9 V
<+1.5 V
±5 V
>−0.9 V
<−1.3 V
+7 V/−2 V
>+1.6 V
<+1.2 V
Table 9. Truth Table for the SHUTDOWN and SLEEP Pins
SHUTDOWN
SLEEP
Low
Low
High
High
Low
High
Low
High
Operating State
Powered down
Powered down
Low power mode
Full power mode
Figure 55 shows the primary noise contributors for the typical
gain configurations. The total output noise (vn_OUT) is the root
sum square of all the noise contributions.
Vn_RF = 4kTRF
Vn
RG
in–
Vn_RS = 4kTRS
RS
in+
+ Vn_OUT
13391-034
Vn_RG = 4kTRG
2

 4kTRG + in− 2 R F 2


where:
k is Boltzmann’s constant.
T is the absolute temperature in degrees Kelvin.
RF and RG are the feedback network resistances, as shown in
Figure 55.
RS is the source resistance, as shown in Figure 55.
in+ and in− represent the amplifier input current noise spectral
density in pA/√Hz.
vn is the amplifier input voltage noise spectral density in
nV/√Hz.
Source resistance noise, amplifier input voltage noise (vn), and
the voltage noise from the amplifier input current noise
(in+ × RS) are all subject to the noise gain term (1 + RF/RG).
NOISE CONSIDERATIONS
RF
]
Figure 56 shows the total referred to input (RTI) noise due to
the amplifier vs. the source resistance. Note that with a
5.9 nV/√Hz input voltage noise and 0.6 pA/√Hz input current
noise, the noise contributions of the amplifier are relatively
small for source resistances from approximately 2.6 kΩ to
47 kΩ.
The Analog Devices, Inc., silicon germanium (SiGe) bipolar
process makes it possible to achieve a low noise of 5.9 nV/√Hz
for the ADA4806-1. This noise is much improved compared to
similar low power amplifiers with a supply current in the range
of hundreds of microamperes.
Figure 55. Noise Sources in Typical Connection
1000
RTI NOISE (nV/√Hz)
TOTAL NOISE
SOURCE RESISTANCE NOISE
AMPLIFIER NOISE
100
10
SOURCE RESISTANCE = 47kΩ
SOURCE RESISTANCE = 2.6kΩ
1
100
1k
10k
100k
SOURCE RESISTANCE (Ω)
Figure 56. RTI Noise vs. Source Resistance
Rev. 0 | Page 19 of 24
1M
13391-051
Mode
Enabled
Shutdown/Sleep
Mode
[
ADA4806-1
Data Sheet
APPLICATIONS INFORMATION
SLEW ENHANCEMENT
5
The ADA4806-1 has an internal slew enhancement circuit that
increases the slew rate as the feedback error voltage increases.
This circuit allows the amplifier to settle a large step response
faster, as shown in Figure 57. This is useful in ADC applications
where multiple input signals are multiplexed. The impact of the
slew enhancement can also be seen in the large signal frequency
response, where larger input signals cause a slight increase in
peaking, as shown in Figure 58.
4
NORMALIZED GAIN (dB)
3
1.5
0
–1
RF = 2.6kΩ, CF = 1pF
–3
RF = 4.99kΩ, CF = 1pF
1M
VOUT = 1V p-p
10M
100M
FREQUENCY (Hz)
13391-106
–6
100k
Figure 59. Peaking in Frequency Response at Selected RF Values
COMPENSATING PEAKING IN LARGE SIGNAL
FREQUENCY RESPONSE
0
–0.5
0
10
20
30
40
50
60
70
80
90
100
TIME (ns)
13391-254
–1.0
At high frequency, the slew enhancement circuit can contribute to
peaking in the large signal frequency response. Figure 59 shows the
effect of a feedback capacitor on the small signal response, whereas
Figure 60 shows that the same technique is effective for reducing
peaking in the large signal response.
6
Figure 57. Step Response with Selected Output Steps
3
2
VS = ±2.5V
G = +1
RL = 2kΩ
NORMALIZED GAIN (dB)
NORMALIZED GAIN (dB)
RF = 1kΩ
–2
0
VIN = 2V p-p
VIN = 200mV p-p
VIN = 632mV p-p
VIN = 400mV p-p
–1
–2
VS = ±2.5V
G = +2
RL = 2 kΩ
VIN = 632mV p-p
0
–3
RF = 2.6kΩ, CF = 0pF
RF = 1kΩ, CF = 0pF
RF = 2.6kΩ, CF = 2.7pF
RF = 1 kΩ, CF = 2 pF
–6
–9
–3
–12
VIN = 100mV p-p
–4
–15
100k
–5
1M
10M
100M
–6
100k
1M
10M
FREQUENCY (Hz)
100M
13391-105
FREQUENCY (Hz)
Figure 58. Peaking in Frequency Responses as Signal Level Changes, G = +1
EFFECT OF FEEDBACK RESISTOR ON FREQUENCY
RESPONSE
The amplifier input capacitance and feedback resistor form a
pole that, for larger value feedback resistors, can reduce phase
margin and contribute to peaking in the frequency response.
Figure 59 shows the peaking for selected feedback resistors (RF)
when the amplifier is configured in a gain of +2. Figure 59 also
shows how peaking can be mitigated with the addition of a
small value capacitor placed across the feedback resistor of the
amplifier.
13391-107
OUTPUT VOLTAGE (V)
1
–5
VOUT = 500mV p-p
1
RF = 4.99kΩ
2
VOUT = 2V p-p
0.5
–1.5
RF = 2.6kΩ
–4
VS = ±2.5V
G = +1
RL = 2kΩ
1.0
VS = ±2.5V
G = +2
RL = 2 kΩ
VIN = 20mV p-p
Figure 60. Peaking Mitigation in Large Signal Frequency Response
DRIVING LOW POWER, HIGH RESOLUTION
SUCCESSIVE APPROXIMATION REGISTER (SAR)
ADCs
The ADA4806-1 is ideal for driving low power, high resolution
SAR ADCs. The 5.9 nV/√Hz input voltage noise and rail-to-rail
output stage of the ADA4806-1 help minimize distortion at
large output levels. With its low power of 500 µA, the amplifier
consumes power that is compatible with low power SAR ADCs,
which are usually in the microwatt (µW) to low milliwatt (mW)
range. Furthermore, the ADA4806-1 supports a single-supply
configuration; the input common-mode range extends to 0.1 V
below the negative supply, and 1 V below the positive supply.
Rev. 0 | Page 20 of 24
Data Sheet
ADA4806-1
Figure 61 shows a typical 16-bit, single-supply application. The
ADA4806-1 drives the AD7980, a 16-bit, 1 MSPS, SAR ADC in
a low power configuration. The AD7980 operates on a 2.5 V
supply and supports an input from 0 V to VREF. In this case, the
ADR435 provides a 5 V reference. The ADA4806-1 is used both
as a driver for the AD7980 and as a reference buffer for the
ADR435.
DYNAMIC POWER SCALING
The low-pass filter formed by R3 and C1 reduces the noise to
the input of the ADC (see Figure 61). In lower frequency
applications, the designer can reduce the corner frequency of
the filter to remove additional noise.
Figure 62 illustrates a method by which the quiescent power of
the ADC driver can be dynamically scaled with the sampling
rate of the system. By providing properly timed signals to the
convert input (CNV) pin of the ADC and the SHUTDOWN
and SLEEP pins of the ADA4806-1, both devices can be run at
optimum efficiency.
+7.5V
5V REF
ADA4806-1
VDD
C2
10µF
C4
100nF
C3
0.1µF
+5V
+6V
+2.5V
0.1µF
VIN
ADA4806-1
+7.5V
ADA4806-1
R3
20Ω
IN+
VDD
AD7980
GND CNV
AD7980
IN–
C1
2.7nF
REF VDD
GND
TIMING
GENERATOR
13391-310
0V TO
VREF
REF
20Ω
2.7nF
Figure 62. ADA4806-1/AD7980 Power Management Circuitry
Figure 61. Driving the AD7980 with the ADA4806-1
In this configuration, the ADA4806-1 consume 7.2 mW of
quiescent power. The measured signal-to-noise ratio (SNR),
THD, and signal-to-noise-and-distortion ratio (SINAD) of the
whole system for a 10 kHz signal are 89.4 dB, 104 dBc, and
89.3 dB, respectively. This translates to an effective number of
bits (ENOB) of 14.5 at 10 kHz, which is compatible with the
AD7980 performance. Table 10 shows the performance of this
setup at selected input frequencies.
Figure 63 illustrates the relative signal timing for power scaling
the ADA4806-1 and the AD7980. To prevent any degradation in
the performance of the ADC, the ADA4806-1 must have a fully
settled output into the ADC before the activation of the
CNV pin. The amplifier on-time (tAMP, ON) is the time the amplifier
is enabled prior to the rising edge of the CNV signal; this time
depends on whether the SHUTDOWN pin or SLEEP pin is being
driven. In the example shown in Figure 64, tAMP, ON is 3 µs for the
SHUTDOWN pin and 0.5 µs for the SLEEP pin. After a
conversion, the SHUTDOWN pin and/or the SLEEP pin of the
ADA4806-1 are pulled low when the ADC input is inactive in
between samples. While in shutdown mode, the ADA4806-1
output impedance is high.
Table 10. System Performance at Selected Input Frequencies for Driving the AD7980 Single-Ended
Input Frequency (kHz)
1
10
20
50
100
ADC Driver
Supply (V)
Gain
7.5
1
7.5
1
7.5
1
7.5
1
7.5
1
13391-330
ADR435
One of the merits of a SAR ADC, like the AD7980, is that its
power scales with the sampling rate. This power scaling makes
SAR ADCs very power efficient, especially when running at a
low sampling frequency. However, the ADC driver used with
the SAR ADC traditionally consumes constant power regardless
of the sampling frequency.
Reference Buffer
Supply (V)
Gain
7.5
1
7.5
1
7.5
1
7.5
1
7.5
1
Rev. 0 | Page 21 of 24
SNR (dB)
89.8
89.4
89.9
88.5
86.3
Results
THD (dBc)
SINAD (dB)
103
89.6
104
89.3
103
89.7
99
88.1
93.7
85.6
ENOB
14.6
14.5
14.6
14.3
13.9
ADA4806-1
Data Sheet
CNV
SAMPLING PERIOD, tS
ACQUISITION
CONVERSION
ACQUISITION
CONVERSION
ACQUISITION
CONVERSION
ADC
POWERED
ON
ADA4806-1
SHUTDOWN/
SLEEP
POWERED
ON
SHUTDOWN/SLEEP
tAMP, ON
SHUTDOWN/SLEEP
tAMP, ON
POWERED
ON
SHUTDOWN/SLEEP
tAMP, ON
IQ, ON
tAMP, OFF
tAMP, OFF
13391-329
ADA4806-1
QUIESCENT
CURRENT
tAMP, OFF
Figure 63. Timing Waveforms
(1)
With power scaling, the quiescent power becomes proportional
to the ratio between the amplifier on time, tAMP, ON, and the
sampling time, tS:
t

PQ =  I Q _ on × VS × AMP ,ON
tS

t −t
 
 +  I Q _ off × VS × S AMP ,ON
tS
 
 (2)


Thus, by dynamically switching the ADA4806-1 between
shutdown/sleep and full power modes between consecutive
samples, the quiescent power of the driver scales with the
sampling rate.
CONTINUOUSLY ON
1.0
SLEEP MODE
0.1
AD7980 ADC
SHUTDOWN MODE
0.01
0.01
0.1
1
10
ADC SAMPLE RATE (ksps)
100
1000
Figure 64. Quiescent Power Consumption of the ADA4806-1 vs.
ADC Sample Rate, Using Dynamic Power Scaling
Note that tAMP, ON in Figure 64 is 3 µs for the SHUTDOWN pin and
0.5 µs for the SLEEP pin.
Rev. 0 | Page 22 of 24
13391-612
P Q = IQ × V S
10
QUIESCENT POWER CONSUMPTION (mW)
Figure 64 shows the quiescent power of the ADA4806-1,
operating from a single +6 V supply, without power scaling and
while power scaling via the SHUTDOWN pin and the SLEEP pin.
Without power scaling, the ADA4806-1 consumes constant
power regardless of the sampling frequency, as shown in
Equation 1.
Data Sheet
ADA4806-1
SINGLE-ENDED TO DIFFERENTIAL CONVERSION
LAYOUT CONSIDERATIONS
Most high resolution ADCs have differential inputs to reduce
common-mode noise and harmonic distortion. Therefore, it is
necessary to use an amplifier to convert a single-ended signal
into a differential signal to drive the ADCs.
To ensure optimal performance, careful and deliberate attention
must be paid to the board layout, signal routing, power supply
bypassing, and grounding.
There are two common ways the user can convert a single-ended
signal into a differential signal: either use a differential
amplifier, or configure two amplifiers as shown in Figure 65.
The use of a differential amplifier yields better performance,
whereas the 2-op-amp solution results in lower system cost. The
ADA4806-1 solves this dilemma of choosing between the two
methods by combining the advantages of both. Its low harmonic
distortion, low offset voltage, and low bias current mean that it can
produce a differential output that is well matched with the
performance of the high resolution ADCs.
It is important to avoid ground in the areas under and around the
input and output of the ADA4806-1. Stray capacitance between
the ground plane and the input and output pads of a device is
detrimental to high speed amplifier performance. Stray
capacitance at the inverting input, together with the amplifier
input capacitance, lowers the phase margin and can cause
instability. Stray capacitance at the output creates a pole in the
feedback loop, which can reduce phase margin and cause the
circuit to become unstable.
Ground Plane
Power Supply Bypassing
Figure 65 shows how the ADA4806-1 converts a single-ended
signal into a differential output. The first amplifier is configured
in a gain of +1 with its output then inverted to produce the
complementary signal. The differential output then drives the
AD7982, an 18-bit, 1 MSPS SAR ADC. To further reduce noise,
the user can reduce the values of R1 and R2. However, note that
this increases the power consumption. The low-pass filter of the
ADC driver limits the noise to the ADC.
Power supply bypassing is a critical aspect in the performance
of the ADA4806-1. A parallel connection of capacitors from
each power supply pin to ground works best. Smaller value
ceramic capacitors offer better high frequency response,
whereas larger value ceramic capacitors offer better low
frequency performance.
Paralleling different values and sizes of capacitors helps to ensure
that the power supply pins are provided with a low ac impedance
across a wide band of frequencies. This is important for minimizing
the coupling of noise into the amplifier—especially when the
amplifier PSRR begins to roll off—because the bypass capacitors
can help lessen the degradation in PSRR performance.
The measured SNR, THD, and SINAD of the whole system for a
10 kHz signal are 93 dB, 113 dBc, and 93 dB, respectively. This
translates to an ENOB of 15.1 at 10 kHz, which is compatible
with the performance of the AD7982. Table 11 shows the
performance of this setup at selected input frequencies.
Place the smallest value capacitor on the same side of the board
as the amplifier and as close as possible to the amplifier power
supply pins. Connect the ground end of the capacitor directly to
the ground plane.
Table 11. System Performance at Selected Input Frequencies
for Driving the AD7982 Differentially
THD
(dBc)
104
113
110
102
96
Results
SINAD
(dB)
93
93
93
91
88
It is recommended that a 0.1 µF ceramic capacitor with a
0508 case size be used. The 0508 case size offers low series
inductance and excellent high frequency performance. Place a
10 µF electrolytic capacitor in parallel with the 0.1 µF capacitor.
Depending on the circuit parameters, some enhancement to
performance can be realized by adding additional capacitors.
Each circuit is different and must be analyzed individually for
optimal performance.
ENOB
15.1
15.1
15.1
14.8
14.3
VDD
R3
22Ω
R2
1kΩ
+7.5V
R1
1kΩ
ADA4806-1
VIN
+2.5V
C1
0.1µF
C2
2.7nF
+7.5V
IN+ REF
IN–
R4
22Ω
ADA4806-1
C4
0.1µF
+5V
VDD
AD7982
C3
2.7nF
13391-053
Input Frequency (kHz)
1
10
20
50
100
SNR
(dB)
93
93
93
92
89
+2.5V
Figure 65. Driving the AD7982 with the ADA4806-1
Rev. 0 | Page 23 of 24
ADA4806-1
Data Sheet
OUTLINE DIMENSIONS
3.00
2.90
2.80
1.70
1.60
1.50
8
7
6
5
1
2
3
4
3.00
2.80
2.60
PIN 1
INDICATOR
0.65 BSC
1.95
BSC
1.45 MAX
0.95 MIN
0.15 MAX
0.05 MIN
0.38 MAX
0.22 MIN
0.22 MAX
0.08 MIN
SEATING
PLANE
8°
4°
0°
0.60
BSC
0.60
0.45
0.30
COMPLIANT TO JEDEC STANDARDS MO-178-BA
12-16-2008-A
1.30
1.15
0.90
Figure 66. 8-Lead Small Outline Transistor Package [SOT-23]
(RJ-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model 1
ADA4806-1ARJZ-R2
ADA4806-1ARJZ-R7
ADA4806-1RJ-EBZ
1
Temperature Range
−40°C to +125°C
−40°C to +125°C
Package Description
8-Lead Small Outline Transistor Package [SOT-23]
8-Lead Small Outline Transistor Package [SOT-23]
Evaluation Board for 8-Lead SOT-23
Z = RoHS Compliant Part.
©2015 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D13391-0-9/15(0)
Rev. 0 | Page 24 of 24
Package Option
RJ-8
RJ-8