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18-Bit, 670 kSPS, Differential
Programmable Input PulSAR
®
ADC
Data Sheet
AD7634
Rev. B
Document Feedbac
k
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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
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Tel: 781.329.4700 ©2007–2012 Analog Devices, Inc. All rights reserved.
Technical Suppor t www.analog.com
FEATURES
Multiple pins/software-programmable input ranges
5 V (10 V p-p), +10 V (20 V p-p), ±5 V (20 V p-p),
±10 V (40 V p-p)
Pins or serial SPI®-compatible input ranges/mode selection
Throughput
670 kSPS (warp mode)
570 kSPS (normal mode)
450 kSPS (impulse mode)
INL: ±1.5 LSB typical, ±2.5 LSB maximum (±9.5 ppm of FSR)
18-bit resolution with no missing codes
Dynamic range: 102.5 dB
SNR: 101 dB @ 2 kHz
THD: −112 dB @ 2kHz
iCMOS® process technology
5 V internal reference: typical drift 3 ppm/°C; TEMP output
No pipeline delay (SAR architecture)
Parallel (18-/16-/8-bit bus) and serial 5 V/3.3 V interface
SPI-/QSPI™-/MICROWIRE™-/DSP-compatible
Power dissipation
180 mW @ 670 kSPS, warp mode
28 mW @ 100 kSPS, impulse mode
10 mW @ 1 kSPS, impulse mode
Pb-free, 48-lead LQFP and 48-Lead LFCSP (7 mm × 7 mm)
APPLICATIONS
CT scanners
High dynamic data acquisition
Σ-Δ replacement
Spectrum analysis
Medical instruments
Instrumentation
Process controls
GENERAL DESCRIPTION
The AD7634 is an 18-bit charge redistribution successive
approximation register (SAR), architecture analog-to-
digital converter (ADC) fabricated on Analog Devices, Inc.’s
iCMOS high voltage process. The device is configured through
hardware or via a dedicated write-only serial configuration port
for input range and operating mode. The AD7634 contains a
high speed 18-bit sampling ADC, an internal conversion clock,
an internal reference (and buffer), error correction circuits, and
both serial and parallel system interface ports. A falling edge on
CNVST
samples the fully differential analog inputs on IN+ and
IN−. The AD7634 features four different analog input ranges and
three different sampling modes. Operation is specified from
−40°C to +85°C.
FUNCTIONAL BLOCK DIAGRAM
18
CONTROL LOGIC AND
CALIBRATION CIRCUITRY
CLOCK
AD7634
DGNDDVDD
AVDD
AGND
REF REFGND
IN+
PD
RESET
CNVST
PDBUF
REFBUFIN
PDREF
REF
TEMP
D[17:0]
BUSY
RD
CS
D0/OB/2C
OGND
OVDD
D2/A1
D1/A0
REF
AMP
SERIAL DATA
PORT
PARALLEL
INTERFACE
SWITCHED
CAP DAC
V
C
C
V
EE
WARP IMPULSE BIPOLAR TEN
SERIAL
CONFIGURATION
PORT
IN–
MODE0 MODE1
06406-001
Figure 1.
Table 1. 48-Lead PulSAR Selection
Input Type
Res
(Bits)
100 to
250
(kSPS)
500 to
570
(kSPS)
570 to
1000
(kSPS)
>1000
(kSPS)
Bipolar 14 AD7951
Differential
Bipolar
14 AD7952
Unipolar
16
AD7651
AD7660
AD7661
AD7650
AD7652
AD7664
AD7666
AD7653
AD7667
Bipolar 16
AD7610
AD7663
AD7665
AD7612
AD7671
Differential
Unipolar
16 AD7675 AD7676 AD7677
AD7621
AD7622
AD7623
Simultaneous/
Multichannel
Unipolar
16
AD7654
AD7655
Differential
Unipolar
18 AD7678 AD7679 AD7674 AD7641
AD7643
Differential
Bipolar
18 AD7631 AD7634
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