18-Bit, 670 kSPS, Differential
Programmable Input PulSAR ADC
Data Sheet
Rev. B
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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
DGND
DVDD
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
VCC VEE
WARP IMPULSE BIPOLAR TEN
SERIAL
CONFIGURATION
PORT
IN–
MODE0
MODE1
06
406
-00
1
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
Differential
Bipolar
14
Unipolar
16
Bipolar
16
Differential
Unipolar
16
Simultaneous/
Multichannel
Unipolar
16
Differential
Unipolar
18
Differential
Bipolar
18
AD7634