250 kSPS, 6-Channel, Simultaneous
Sampling, Bipolar 16-/14-/12-Bit ADC
AD7656/AD7657/AD7658
FUNCTIONAL BLOCK DIAGRAM
FEATURES
V
CONVST A
CONVST B CONVST C AV
DV
DD
CC
CC
6 independent ADCs
True bipolar analog inputs
CS
Pin-/software-selectable ranges: ±10 V, ±± V
Fast throughput rate: 2±0 kSPS
iCMOSTM process technology
Low power
140 mW at 2±0 kSPS with ± V supplies
Wide input bandwidth
86.± dB SNR at ±0 kHz input frequency
On-chip reference and reference buffers
Parallel, serial, and daisy-chain interface modes
High speed serial interface
SPI®-/QSPI™-/MICROWIRE™-/DSP-compatible
Standby mode: 100 μW maximum
64-lead LQFP
CLK
REF
SER/PAR
CONTROL
LOGIC
OSC
V
DRIVE
STBY
BUF
BUF
BUF
OUTPUT
DRIVERS
DOUT A
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
T/H
V1
V2
V3
V4
V5
V6
SCLK
T/H
T/H
T/H
T/H
OUTPUT
DRIVERS
DOUT B
OUTPUT
DRIVERS
DOUT C
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
DATA/
CONTROL
LINES
OUTPUT
DRIVERS
RD
WR
T/H
V
APPLICATIONS
AD7656/AD7657/AD7658
Power line monitoring systems
Instrumentation and control systems
Multi-axis positioning systems
AGND
DGND
SS
Figure 1.
GENERAL DESCRIPTION
The AD7656/AD7657/AD76581 contain six 16-/14-/12-bit, fast,
low power, successive approximation ADCs all in the one
package that is designed on the iCMOS process (industrial
CMOS). iCMOS is a process combining high voltage silicon
with submicron CMOS and complementary bipolar
technologies. It enables the development of a wide range of high
performance analog ICs, capable of 33 V operation in a
footprint that no previous generation of high voltage parts
could achieve. Unlike analog ICs using conventional CMOS
processes, iCMOS components can accept bipolar input signals
while providing increased performance, which dramatically
reduces power consumption and package size.
The conversion process and data acquisition are controlled
using CONVST signals and an internal oscillator. Three
CONVST pins allow independent, simultaneous sampling of
the three ADC pairs. The AD7656/AD7657/AD7658 all have a
high speed parallel and serial interface, allowing the devices to
interface with microprocessors or DSPs. In serial interface
mode, the parts have a daisy-chain feature that allows multiple
ADCs to connect to a single serial interface. The AD7656/
AD7657/AD7658 can accommodate true bipolar input signals
in the 4 ꢀ VREF range and 2 ꢀ VREF range. The AD7656/
AD7657/AD7658 also contain an on-chip 2.5 V reference.
PRODUCT HIGHLIGHTS
The AD7656/AD7657/AD7658 feature throughput rates up
to 250 kSPS. The parts contain low noise, wide bandwidth,
track-and-hold amplifiers that can handle input frequencies
up to 12 MHz.
1. Six 16-/14-/12-bit, 250 kSPS ADCs on board.
2. Six true bipolar, high impedance analog inputs.
3. Parallel and high speed serial interfaces.
1 Protected by U.S. Patent No. 6,731,232.
Rev. A
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