2
LC MOS 4-Channel, 12-Bit Simultaneous
a
Sampling Data Acquisition System
AD7874
FEATURES
FUNCTIO NAL BLO CK D IAGRAM
Four On-Chip Track/ Hold Am plifiers
Sim ultaneous Sam pling of 4 Channels
Fast 12-Bit ADC w ith 8 s Conversion Tim e/ Channel
29 kHz Sam ple Rate for All Four Channels
On-Chip Reference
VDD VDD
INT CS
RD CONVST
INTERNAL
CLOCK
CONTROL LOGIC
CLK
TRACK/
HOLD 1
V
؎10 V Input Range
IN1
؎5 V Supplies
TRACK/
HOLD 2
V
COMP
IN2
APPLICATIONS
Sonar
Motor Controllers
Adaptive Filters
Digital Signal Processing
MUX
SAR
TRACK/
HOLD 3
V
IN3
DATA
DB0
REGISTERS
DB11
TRACK/
HOLD 4
V
IN4
REFERENCE
BUFFER
12-BIT
DAC
REF IN
AD7874
GENERAL D ESCRIP TIO N
3V
REFERENCE
REF OUT
T he AD7874 is a four-channel simultaneous sampling, 12-bit
data acquisition system. T he part contains a high speed 12-bit
ADC, on-chip reference, on-chip clock and four track/hold am-
plifiers. T his latter feature allows the four input channels to be
sampled simultaneously, thus preserving the relative phase
information of the four input channels, which is not possible if
all four channels share a single track/hold amplifier. T his makes
the AD7874 ideal for applications such as phased-array sonar
and ac motor controllers where the relative phase information is
important.
VSS
AGND DGND
P RO D UCT H IGH LIGH TS
1. Simultaneous Sampling of Four Input Channels.
Four input channels, each with its own track/hold amplifier,
allow simultaneous sampling of input signals. T rack/hold ac-
quisition time is 2 µs, and the conversion time per channel is
8 µs, allowing 29 kHz sample rate for all four channels.
T he aperture delay of the four track/hold amplifiers is small and
specified with minimum and maximum limits. T his allows sev-
eral AD7874s to sample multiple input channels simultaneously
without incurring phase errors between signals connected to
several devices. A reference output/reference input facility also
allows several AD7874s to be driven from the same reference
source.
2. T ight Aperture Delay Matching.
T he aperture delay for each channel is small and the aperture
delay matching between the four channels is less than 4 ns.
Additionally, the aperture delay specification has upper and
lower limits allowing multiple AD7874s to sample more than
four channels.
3. Fast Microprocessor Interface.
In addition to the traditional dc accuracy specifications such as
linearity, full-scale and offset errors, the AD7874 is also fully
specified for dynamic performance parameters including distor-
tion and signal-to-noise ratio.
T he high speed digital interface of the AD7874 allows direct
connection to all modern 16-bit microprocessors and digital
signal processors.
T he AD7874 is fabricated in Analog Devices’ Linear Compat-
ible CMOS (LC2MOS) process, a mixed technology process
that combines precision bipolar circuits with low-power CMOS
logic. T he part is available in a 28-pin, 0.6" wide, plastic or her-
metic dual-in-line package (DIP), in a 28-terminal leadless ce-
ramic chip carrier (LCCC) and in a 28-pin SOIC.
REV. C
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norw ood, MA 02062-9106, U.S.A.
Tel: 617/ 329-4700
Fax: 617/ 326-8703