Ultralow Power, Low Distortion,
Fully Differential ADC Drivers
ADA4940-1/ADA4940-2
Data Sheet
FEATURES
FUNCTIONAL BLOCK DIAGRAMS
13 –VS
14 –VS
16 –VS
–FB 1
12 DISABLE
+IN 2
11 –OUT
–IN 3
10 +OUT
9
VOCM
NOTES
1. CONNECT THE EXPOSED PAD TO
–VS OR GROUND.
08452-001
+VS 8
+VS 7
+VS 6
+VS 5
+FB 4
Low power PulSAR®/SAR ADC drivers
Single-ended-to-differential conversion
Differential buffers
Line drivers
Medical imaging
Industrial process controls
Portable electronics
19 –OUT1
21 –VS1
20 DISABLE1
24 +IN1
23 –FB1
22 –VS1
Figure 1. ADA4940-1
APPLICATIONS
18 +OUT1
17 VOCM1
16 –VS2
–IN1 1
+FB1 2
+VS1 3
ADA4940-2
+VS1 4
15 –VS2
With the ADA4940-1/ADA4940-2, differential gain configurations
are easily realized with a simple external feedback network of
four resistors determining the closed-loop gain of the amplifier.
The ADA4940-1/ADA4940-2 are fabricated using 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 excellent dynamic
performance of the ADA4940-1/ADA4940-2 make them well
suited for a variety of data acquisition and signal processing
applications.
+OUT2 12
NOTES
1. CONNECT THE EXPOSED PAD TO
–VS OR GROUND.
07429-202
The ADA4940-1/ADA4940-2 are low noise, low distortion fully
differential amplifiers with very low power consumption. They
are an ideal choice for driving low power, high resolution, high
performance SAR and 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 commonmode voltage allows the 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.
+VS2 10
13 –OUT2
VOCM2 11
+IN2 6
–IN2 7
14 DISABLE1
+FB2 8
+VS2 9
–FB2 5
GENERAL DESCRIPTION
Rev. D
15 –VS
ADA4940-1
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
ADA4940-1 is available in LFCSP and SOIC packages
Figure 2. ADA4940-2
The ADA4940-1 is available in a 3 mm × 3 mm, 16-lead LFCSP
and an 8-lead SOIC. The ADA4940-2 is available in a 4 mm ×
4 mm, 24-lead LFCSP. The pinouts are optimized to facilitate
printed circuit board (PCB) layout and minimize distortion.
The ADA4940-1/ADA4940-2 are specified to operate over the
−40°C to +125°C temperature range.
Table 1. Similar Products to ADA4940-1/ADA4940-2
Product
AD8137
ADA4932-1
ADA4941-1
ISUPPLY
(mA)
3
9
2.2
Bandwidth
(MHz)
110
560
31
Slew Rate
(V/μs)
450
2800
22
Noise
(nV/√Hz)
8.25
3.6
5.1
Table 2. Complementary Products to ADA4940-1/ADA4940-2
Product
AD7982
AD7984
AD7621
AD7623
Power
(mW)
7.0
10.5
65
45
Throughput
(MSPS)
1
1.333
3
1.333
Resolution
(Bits)
18
18
16
16
SNR
(dB)
98
96.5
88
88
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