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AD7894
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 1998
5 V, 14-Bit Serial, 5 s
ADC in SO-8 Package
FUNCTIONAL BLOCK DIAGRAM
SIGNAL
SCALING*
TRACK/
HOLD
14-BIT
ADC
AD7894
OUTPUT
REGISTER
REF IN
V
DD
V
IN
CONVST
GND BUSY SCLK SDATA
*AD7894-10, AD7894-3
FEATURES
Fast 14-Bit ADC with 5 s Conversion Time
8-Lead SOIC Package
Single 5 V Supply Operation
High Speed, Easy-to-Use, Serial Interface
On-Chip Track/Hold Amplifier
Selection of Input Ranges
ⴞ10 V for AD7894-10
ⴞ2.5 V for AD7894-3
0 V to +2.5 V for AD7894-2
High Input Impedance
Low Power: 20 mW Typ
Pin Compatible Upgrade of 12-Bit AD7895
GENERAL DESCRIPTION
The AD7894 is a fast, 14-bit ADC that operates from a single
+5 V supply and is housed in a small 8-lead SOIC. The part
contains a 5 µs successive approximation A/D converter, an on-
chip track/hold amplifier, an on-chip clock and a high speed
serial interface.
Output data from the AD7894 is provided via a high speed,
serial interface port. This two-wire serial interface has a serial
clock input and a serial data output with the external serial clock
accessing the serial data from the part.
In addition to the traditional dc accuracy specifications such as
linearity, full-scale and offset errors, the AD7894 is also speci-
fied for dynamic performance parameters including harmonic
distortion and signal-to-noise ratio.
The part accepts an analog input range of ±10 V (AD7894-10),
±2.5 V (AD7894-3), 0 V to +2.5 V (AD7894-2), and operates
from a single +5 V supply consuming only 20 mW typical.
The AD7894 features a high sampling rate mode and, for low
power applications, a proprietary automatic power-down mode
where the part automatically goes into power-down once conver-
sion is complete and “wakes up” before the next conversion
cycle.
The part is available in a small outline IC (SOIC).
PRODUCT HIGHLIGHTS
1. Fast, 14-Bit ADC in 8-Lead Package
The AD7894 contains a 5␣ µs ADC, a track/hold amplifier,
control logic and a high speed serial interface, all in an 8-lead
package. This offers considerable space saving over alterna-
tive solutions.
2. Low Power, Single Supply Operation
The AD7894 operates from a single +5 V supply and con-
sumes only 20 mW. The automatic power-down mode,
where the part goes into power-down once conversion is
complete and “wakes up” before the next conversion cycle,
makes the AD7894 ideal for battery powered or portable
applications.
3. High Speed Serial Interface
The part provides high speed serial data and serial clock lines
allowing for an easy, two-wire serial interface arrangement.
