FUNCTIONAL BLOCK DIAGRAMS
REV. 0
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reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
LC
2
MOS
Dual 12-Bit DACPORTs
AD7237A/AD7247A
FEATURES
Complete Dual 12-Bit DAC Comprising
Two 12-Bit CMOS DACs
On-Chip Voltage Reference
Output Amplifiers
Reference Buffer Amplifiers
Improved AD7237/AD7247:
12 V to 15 V Operation
Faster Interface –30 ns typ Data Setup Time
Parallel Loading Structure: AD7247A
(8+4) Loading Structure: AD7237A
Single or Dual Supply Operation
Low Power—165 mW typ in Single Supply
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
PRODUCT HIGHLIGHTS
1. The AD7237A/AD7247A is a dual 12-bit DACPORT
®
on a
single chip. This single chip design and small package size
offer considerable space saving and increased reliability over
multichip designs.
2. The improved interface times of the parts allow easy, direct
interfacing to most modern microprocessors, whether they
have 8-bit or 16-bit data bus structures.
3. The AD7237A/AD7247A features a wide power supply
range allowing operation from 12 V supplies.
DACPORT is a registered trademark of Analog Devices, Inc.
GENERAL DESCRIPTION
The AD7237A/AD7247A is an enhanced version of the industry
standard AD7237/AD7247. Improvements include operation
from 12 V to 15 V supplies, faster interface times and better
reference variations with V
DD
. Additional features include faster
settling times.
The AD7237A/AD7247A is a complete, dual, 12-bit, voltage
output digital-to-analog converter with output amplifiers and
Zener voltage reference on a monolithic CMOS chip. No exter-
nal user trims are required to achieve full specified performance.
Both parts are microprocessor compatible, with high speed data
latches and interface logic. The AD7247A accepts 12-bit paral-
lel data which is loaded into the respective DAC latch using the
WR input and a separate Chip Select input for each DAC. The
AD7237A has a double buffered interface structure and an 8-bit
wide data bus with data loaded to the respective input latch in
two write operations. An asynchronous
LDAC signal on the
AD7237A updates the DAC latches and analog outputs.
A REF OUT/REF IN function is provided which allows either
the on-chip 5 V reference or an external reference to be used as
a reference voltage for the part. For single supply operation, two
output ranges of 0 V to +5 V and 0 V to +10 V are available,
while these two ranges plus an additional ±5 V range are avail-
able with dual supplies. The output amplifiers are capable of de-
veloping +10 V across a 2 kΩ load to GND.
The AD7237A/AD7247A is fabricated in Linear Compatible
CMOS (LC
2
MOS), an advanced, mixed technology process
that combines precision bipolar circuits with low power CMOS
logic. Both parts are available in a 24-pin, 0.3" wide plastic and
hermetic dual-in-line package (DIP) and are also packaged in a
24-lead small outline (SOIC) package.
