REV. A
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a
AD7851
© Analog Devices, Inc., 1996
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
FUNCTIONAL BLOCK DIAGRAM
AIN (+)
AIN (–)
C
REF1
C
REF2
CAL
AV
DD AGND AGND
DV
DD
DGND
AMODE
CLKIN
SLEEP
CONVST
BUSY
SYNCSM1 SM2 DIN DOUT SCLK POLARITY
CHARGE
REDISTRIBUTION
DAC
COMP
4.096 V
REFERENCE
AD7851
BUF
T/H
SAR + ADC
CONTROL
CALIBRATION
MEMORY
AND CONTROLLER
SERIAL INTERFACE / CONTROL REGISTER
REF
IN
/
REF
OUT
14-Bit 333 kSPS
Serial A/D Converter
FEATURES
Single 5 V Supply
333 kSPS Throughput Rate/62 LSB DNL—A Grade
285 kSPS Throughput Rate/61 LSB DNL—K Grade
A & K Grades Guaranteed to 1258C/238 kSPS
Throughput Rate
Pseudo-Differential Input with Two Input Ranges
System and Self-Calibration with Autocalibration on
Power-Up
Read/Write Capability of Calibration Data
Low Power: 60 mW typ
Power-Down Mode: 5 mW typ Power Consumption
Flexible Serial Interface:
8051/SPI/QSPI/ mP Compatible
24-Pin DIP, SOIC and SSOP Packages
APPLICATIONS
Digital Signal Processing
Speech Recognition and Synthesis
Spectrum Analysis
DSP Servo Control
Instrumentation and Control Systems
High Speed Modems
Automotive
GENERAL DESCRIPTION
The AD7851 is a high speed, 14-bit ADC that operates from a
single 5 V power supply. The ADC powers-up with a set of
default conditions at which time it can be operated as a read-
only ADC. The ADC contains self-calibration and system-
calibration options to ensure accurate operation over time and
temperature and has a number of power-down options for low
power applications.
The AD7851 is capable of 333 kHz throughput rate. The input
track-and-hold acquires a signal in 0.33 µs and features a
pseudo-differential sampling scheme. The AD7851 has the
added advantage of two input voltage ranges (0 V to V
REF,
and
–V
REF
/2 to +V
REF
/2 centered about V
REF
/2). Input signal range
is to V
DD
and the part is capable of converting full-power signals
to 20 MHz.
CMOS construction ensures low power dissipation (60 mW typ)
with power-down mode (5 µW typ). The part is available in 24-
pin, 0.3 inch-wide dual-in-line package (DIP), 24-lead small
outline (SOIC) and 24-lead small shrink outline (SSOP) packages.
*Patent pending.
See Page 35 for data sheet index.
PRODUCT HIGHLIGHTS
1. Single 5 V supply.
2. Operates with reference voltages from 4 V to V
DD
.
3. Analog input ranges from 0 V to V
DD
.
4. System and self-calibration including power-down mode.
5. Versatile serial I/O port.