Ultralow Power, Low Distortion
Fully Differential ADC Driver
Data Sheet
Rev. C
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FEATURES
Small signal bandwidth: 260 MHz
Ultralow power 1.25mA
Extremely low harmonic distortion
122 dB THD at 50 kHz
96 dB THD at 1 MHz
Low input voltage noise: 3.9 nV/√Hz
0.35 mV maximum offset voltage
Balanced outputs
Settling time to 0.1%: 34 ns
Rail-to-rail output: VS + 0.1 V to +VS 0.1 V
Adjustable output common-mode voltage
Flexible power supplies: 3 V to 7 V (LFCSP)
Disable pin to reduce power consumption
APPLICATIONS
Low power PulSAR/SAR ADC drivers
Single-ended-to-differential conversion
Differential buffers
Line drivers
Medical imaging
Industrial process controls
Portable electronics
GENERAL DESCRIPTION
differential amplifiers with very low power consumption. They
are an ideal choice for driving low power, high resolution, high
performance SAR and sigma-delta (Σ-Δ) analog-to-digital
converters (ADCs) with resolutions up to 16 bits from dc to
1 MHz on only 1.25 mA of quiescent current. The adjustable
level of the output common-mode voltage allows th
e ADA4940-1/ADA4940-2 to match the input common-mode voltage of
multiple ADCs. The internal common-mode feedback loop
provides exceptional output balance, as well as suppression of
even-order harmonic distortion products.
configurations are easily realized with a simple external feedback
network of four resistors determining the closed-loop gain of
Analog Devices, Inc., SiGe complementary bipolar process,
enabling them to achieve very low levels of distortion with an
input voltage noise of only 3.9 nV/√Hz. The low dc offset and
make them well suited for a variety of data acquisition and signal
processing applications.
FUNCTIONAL BLOCK DIAGRAMS
1
–FB
2
+IN
3
–IN
4
+FB
11 –OUT
12 DISABLE
10 +OUT
9
VOCM
5
+V
S
6
+V
S
7
+V
S
8
+V
S
15
–V
S
16
–V
S
14
–V
S
13
–V
S
ADA4940-1
08452-
001
ADA4940-2
1
–IN1
2
+FB1
3
+VS1
4
+VS1
5
–FB2
6
+IN2
15 –VS2
16 –VS2
17 VOCM1
18 +OUT1
14 DISABLE2
13 –OUT2
7
–
IN2
8
+
F
B2
9
+V
S
2
11
V
OC
M
2
12
+
O
UT
2
10
+V
S
2
21
–V
S
1
22
–V
S
1
23
–
F
B1
24
+
IN1
20
DI
S
ABL
E
1
19
–
O
UT
1
Figure 1.
0
–160
–140
–120
–100
–80
–60
–40
–20
0
20k
40k
60k
80k
100k
08452-
300
AM
P
L
IT
UDE
(
d
B)
FREQUENCY (Hz)
+DIN
–DIN
R1
R2
R4
R3
+IN
–OUT
CF
33
2.5V
AD7982
ADA4940-1
33
2.7nF
CF
+OUT
+
–
–IN
IN+
IN– GND
VDD
REF
VOCM
free, 4 mm × 4 mm, 24-lead LFCSP. The pinout is optimized to
facilitate printed circuit board (PCB) layout and minimize
operate over the 40°C to +125°C temperature range.
Product
Isupply
(mA)
Bandwidth
(MHz)
Slew Rate
(V/s)
Noise
(nV/√Hz)
3
110
450
8.25
9
560
2800
3.6
2.2
31
22
5.1
Product
Power
(mW)
Throughput
(MSPS)
Resolution
(Bits)
SNR
(dB)
7.0
1
18
98
10.5
1.333
18
96.5
65
3
16
88
45
1.333
16
88