AD7898
*
a
5 V, 12-Bit, Serial 220 kSPS
ADC in an 8-Lead Package
REV. A
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FUNCTIONAL BLOCK DIAGRAM
SIGNAL
SCALING*
12-BIT
ADC
TRACK/HOLD
AD7898
V
DD
REF IN
V
IN
CONVST
GND
VDRIVE
SCLK
SDATA
*AD7898-10, AD7898-3
OUTPUT
REGISTER
FEATURES
Fast 12-Bit ADC with 220 kSPS Throughput Rate
8-Lead SOIC
Single 5 V Supply Operation
High Speed, Flexible, Serial Interface that
Allows Interfacing to 3 V Processors
On-Chip Track/Hold Amplifier
Selection of Input Ranges
ⴞ10 V for AD7898-10
ⴞ2.5 V for AD7898-3
High Input Impedance
Low Power: 22.5 mW Max
GENERAL DESCRIPTION
The AD7898 is a fast 12-bit ADC that operates from a single
5V supply and is housed in a small 8-lead SOIC package. The
part contains a successive approximation A/D converter, an on-
chip track/hold amplifier, an on-chip clock, and a high speed
serial interface.
The AD7898 offers two modes of operation. In Mode 0, con-
version is initiated by the CONVST input and the conversion
process is controlled by an internal clock oscillator. In this mode,
the serial interface consists of three wires and the AD7898 is
capable of throughput rates up to 220 kSPS. In Mode 1, the
conversion process is controlled by an externally applied SCLK
with data being accessed from the part during conversion. In
this mode, the serial interface consists of three wires and the
AD7898 is capable of throughput rates up to 220 kSPS.
In addition to the traditional dc accuracy specifications, such as
linearity and full-scale and offset errors, the AD7898 is specified
for dynamic performance parameters, including harmonic dis-
tortion and signal-to-noise ratio.
The part accepts an analog input range of ± 10 V (AD7898-10)
and ± 2.5 V (AD7898-3), and operates from a single 5 V supply,
consuming only 22.5 mW max.
The part is available in an 8-lead Standard Small Outline
Package (SOIC).
PRODUCT HIGHLIGHTS
1. Fast, 12-Bit ADC in 8-Lead Package
The AD7898 contains a 220 kSPS ADC, a track/hold ampli-
fier, control logic, and a high speed serial interface, all in an
8-lead package. This offers considerable space saving over
alternative solutions.
2. Low Power, Single-Supply Operation
The AD7898 operates from a single 5 V supply and con-
sumes only 22.5 mW. The V
DRIVE
function allows the serial
interface to connect directly to either 3 V or 5 V processor
systems independent of V
DD
.
3. Flexible, High Speed Serial Interface
The part provides a flexible, high speed serial interface that
has two distinct modes of operation. Mode 0 provides a three-
wire interface with data being accessed from the AD7898
when conversion is complete. Mode 1 offers a three-wire
interface with data being accessed during conversion.
4. Power-Down Mode
The AD7898 offers a proprietary power-down capability
when operated in Mode 1, making the part ideal for portable
or hand-held applications.
*Protected by U.S. Patent No. 6,681,332
