FEATURES
TYPICAL APPLICATIONS CIRCUIT
APPLICATIONS
High resolution, high precision analog-to-digital converter
(ADC) drivers
Battery-powered instrumentation
Micropower active filters
Portable point of sales terminals
Active RFID readers
Photo multipliers
ADC reference buffers
GENERAL DESCRIPTION
The ADA4805-1/ADA4805-2 are high speed voltage feedback,
rail-to-rail output amplifiers with an exceptionally low
quiescent current of 500 µA, making them ideal for low power,
high resolution data conversion systems. Despite being low
power, these amplifiers provide excellent overall performance.
They offer a high bandwidth of 105 MHz at a gain of +1, a high
slew rate of 160 V/µs, and a low input offset voltage of 125 µV
(maximum).
A shutdown pin allows further reduction of the quiescent
supply current to 2.9 µA. For power sensitive applications, the
shutdown mode offers a very fast turn-on time of 3 µs. This
allows the user to dynamically manage the power of the
amplifier by turning the amplifier off between ADC samples.
Rev. B
+7.5V
5V REF
ADA4805-1/
ADA4805-2
ADR435
VDD
C2
10µF
C4
100nF
C3
0.1µF
+7.5V
ADA4805-1/
ADA4805-2
R3
20Ω
IN+
AD7980
IN–
C1
2.7nF
REF VDD
GND
11345-010
0V TO
VREF
Figure 1. Driving the AD7980 with the ADA4805-1/ADA4805-2
The Analog Devices, Inc., proprietary extra fast complementary
bipolar (XFCB) process allows both low voltage and low current
noise (5.9 nV/√Hz, 0.6 pA/√Hz). The ADA4805-1/ADA4805-2
operate over a wide range of supply voltages from ±1.5 V to
±5 V, as well as single 3 V and 5 V supplies, making them ideal
for high speed, low power instruments.
The ADA4805-1 is available in a 6-lead SOT-23 and a 6-lead
SC70 package. The ADA4805-2 is available in an 8-lead MSOP
and a 10-lead LFCSP package. These amplifiers are rated to
work over the industrial temperature range of −40°C to +125°C.
0
INPUT FREQUENCY = 10kHz
SNR = 89.4dB
THD = 104dB
SINAD = 89.3dB
–20
–40
AMPLITUDE (dB)
Low input offset voltage: 125 µV (maximum)
Low input offset voltage drift
0.2 µV/°C (typical)
1.5 µV/°C (maximum)
Ultralow supply current: 500 µA per amplifier
Fully specified at VS = 3 V, 5 V, ±5 V
High speed performance
−3 dB bandwidth: 105 MHz
Slew rate: 160 V/µs
Settling time to 0.1%: 35 ns
Rail-to-rail outputs
Input common-mode range: −VS − 0.1 V to +VS − 1 V
Low noise: 5.9 nV/√Hz at 100 kHz; 0.6 pA/√Hz at 100 kHz
Low distortion: −102 dBc/−126 dBc HD2/HD3 at 100 kHz
Low input bias current: 470 nA (typical)
Dynamic power scaling
Turn-on time: 3 µs (maximum) fully settled
Small packaging
6-lead SC70, 6-lead SOT-23, and 8-lead MSOP
–60
–80
–100
–120
–140
–160
–180
0
10
20
30
50
40
FREQUENCY (kHz)
60
70
80
11345-102
Data Sheet
0.2 µV/°C Offset Drift, 105 MHz Low Power,
Low Noise, Rail-to-Rail Amplifiers
ADA4805-1/ADA4805-2
Figure 2. FFT Plot for the Circuit Configuration in Figure 1
Table 1. Complementary ADCs to the ADA4805-1/ADA4805-2
Product
AD7982
AD7984
AD7980
AD7685
ADC Power (mW)
7.0
10.5
4.0
10
Throughput
(MSPS)
1
1.33
1
0.25
Resolution
(Bits)
18
18
16
16
SNR
(dB)
98
98.5
91
88
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ADA4805-1/ADA4805-2
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Amplifier Description................................................................ 18
Applications ....................................................................................... 1
Input Protection ......................................................................... 18
General Description ......................................................................... 1
Shutdown 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...................................................................................... 5
Absolute Maximum Ratings............................................................ 7
Thermal Resistance ...................................................................... 7
Maximum Power Dissipation ..................................................... 7
ESD Caution .................................................................................. 7
Pin Configurations and Function Descriptions ........................... 8
Typical Performance Characteristics ........................................... 10
Test Circuits ..................................................................................... 17
Driving Low Power, High Resolution Successive
Approximation Register (SAR) ADCs..................................... 20
Dynamic Power Scaling............................................................. 21
Single-Ended to Differential Conversion ................................... 23
Layout Considerations ............................................................... 23
Outline Dimensions ....................................................................... 24
Ordering Guide .......................................................................... 25
Theory of Operation ...................................................................... 18
REVISION HISTORY
12/14—Rev. A to Rev. B
Added 10-Lead LFCSP....................................................... Universal
Changes to SHUTDOWN Current Parameter, Table 2 ................ 3
Changes to SHUTDOWN Current Parameter, Table 3 ................ 5
Changes to SHUTDOWN Current Parameter, Table 4 ................ 6
Changes to Table 6 and Figure 3 ...................................................... 7
Changes to Table 8 ............................................................................. 9
Added Figure 6, Renumbered Sequentially ................................... 9
Added Figure 42...............................................................................16
Changed Layout ...............................................................................16
Changes to Shutdown Operation Section ....................................18
Changes to Dynamic Power Scaling Section and Figure 61 ......21
Changes to Figure 62 and Figure 63 ..............................................22
Updated Outline Dimensions ........................................................25
Changes to Ordering Guide ...........................................................25
9/14—Rev. 0 to Rev. A
Added ADA4805-2 ............................................................. Universal
Changes to Features Section, General Description Section, and
Table 1 ................................................................................................. 1
Changes to Table 2 ............................................................................. 3
Changes to Table 3 ............................................................................. 4
Changes to Table 4 ............................................................................. 5
Changes to Table 6 and Figure 3 ...................................................... 7
Added Figure 6; Renumbered Sequentially; and Table 8;
Renumbered Sequentially................................................................. 8
Changes to Figure 7 Caption, Figure 8 Caption, Figure 9
Caption, Figure 10 Caption, and Figure 11 Caption..................... 9
Changes to Figure 13 Caption, Figure 14, Figure 17, and
Figure 18 ........................................................................................... 10
Change to Figure 29 ........................................................................ 12
Moved Figure 41 .............................................................................. 15
Changes to Figure 42....................................................................... 15
Added Figure 43 .............................................................................. 15
Changes to Figure 47 and Figure 48.............................................. 16
Changes to Amplifier Description Section, Input Protection
Section, Shutdown Operation Section, and Figure 51................ 17
Changes to Noise Considerations Section and Figure 52 .......... 18
Changes to Effect of Feedback Resistor on Frequency Response
Section, Compensating Peaking in Large Signal Frequency
Response Section, Figure 57, and Driving Low Power, High
Resolution Successive Approximation Register (SAR) ADC
Section............................................................................................... 19
Changes to Figure 58, Dynamic Power Scaling Section,
Figure 59, and Table 10 ................................................................... 20
Change to Figure 60 ........................................................................ 21
Changes to Single-Ended to Differential Conversion Section,
Table 11, and Figure 62 ................................................................... 22
Updated Outline Dimensions, Figure 65 ..................................... 24
Changes to Ordering Guide ........................................................... 24
7/14—Revision 0: Initial Version
Rev. B | Page 2 of 25
Data Sheet
ADA4805-1/ADA4805-2
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. All specifications are per
amplifier.
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/HD31
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 Drift2
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
OUTPUT CHARACTERISTICS
Output Overdrive Recovery Time
(Rising/Falling Edge)
Output Voltage Swing
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
TMIN to TMAX, 4 σ
VOUT = −4.0 V to +4.0 V
107
13
0.2
550
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 90% of final VOUT
−1.0
VIN = +6 V to −6 V, G = +2
RL = 2 kΩ
Rev. B | Page 3 of 25
130
MΩ
kΩ
pF
V
dB
−0.9
V
V
+4
0.2
0.02
1.25
1.0
2.75
µA
µA
µs
2
3
µs
95/100
−4.98
µV
µV/°C
nA
nA
dB
ns
+4.98
V
ADA4805-1/ADA4805-2
Parameter
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
Sinking/sourcing
