a
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
؎10 V for AD7898-10
؎2.5 V for AD7898-3
High Input Impedance
Low Power: 22.5 mW Max
5 V, 12-Bit, Serial 220 kSPS
ADC in an 8-Lead Package
AD7898*
FUNCTIONAL BLOCK DIAGRAM
VDD
REF IN
AD7898
TRACK/HOLD
V IN
SIGNAL
SCALING*
12-BIT
ADC
OUTPUT
REGISTER
CONVST
GND
VDRIVE
*AD7898-10, AD7898-3
SCLK
SDATA
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The AD7898 is a fast 12-bit ADC that operates from a single
5 V supply and is housed in a small 8-lead SOIC package. The
part contains a successive approximation A/D converter, an onchip track/hold amplifier, an on-chip clock, and a high speed
serial interface.
1. Fast, 12-Bit ADC in 8-Lead Package
The AD7898 contains a 220 kSPS 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
alternative solutions.
The AD7898 offers two modes of operation. In Mode 0, conversion 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.
2. Low Power, Single-Supply Operation
The AD7898 operates from a single 5 V supply and consumes only 22.5 mW. The VDRIVE function allows the serial
interface to connect directly to either 3 V or 5 V processor
systems independent of VDD.
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 distortion 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.
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 threewire 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.
The part is available in an 8-lead Standard Small Outline
Package (SOIC).
*Protected by U.S. Patent No. 6,681,332
REV. A
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may result from its use. No license is granted by implication or otherwise
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