a
FEATURES
Two 12-Bit MDACs with Output Amplifiers
4-Quadrant Multiplication
Space-Saving 0.3" 24-Lead DIP and 24-Terminal
,
SOIC Package
Parallel Loading Structure: AD7847
(8 + 4) Loading Structure: AD7837
APPLICATIONS
Automatic Test Equipment
Function Generation
Waveform Reconstruction
Programmable Power Supplies
Synchro Applications
LC MOS
Complete, Dual 12-Bit MDACs
AD7837/AD7847
FUNCTIONAL BLOCK DIAGRAMS
V
DD
2
MS INPUT
LATCH
LS INPUT
LATCH
8
12
R
FBA
V
OUTA
AGNDA
R
FBB
AD7837
4
DAC LATCH A
V
REFA
V
REFB
DB0
DB7
LDAC
CS
WR
A0
CONTROL
LOGIC
4
DAC A
DAC B
12
DAC LATCH B
8
LS INPUT
LATCH
MS INPUT
LATCH
V
OUTB
AGNDB
GENERAL DESCRIPTION
A1
The AD7837/AD7847 is a complete, dual, 12-bit multiplying
digital-to-analog converter with output amplifiers on a mono-
lithic CMOS chip. No external user trims are required to
achieve full specified performance.
Both parts are microprocessor compatible, with high speed data
latches and interface logic. The AD7847 accepts 12-bit parallel
data which is loaded into the respective DAC latch using the
WR
input and a separate Chip Select input for each DAC. The
AD7837 has a double-buffered 8-bit bus interface structure
with data loaded to the respective input latch in two write opera-
tions. An asynchronous
LDAC
signal on the AD7837 updates
the DAC latches and analog outputs.
The output amplifiers are capable of developing
±
10 V across a
2 kΩ load. They are internally compensated with low input off-
set voltage due to laser trimming at wafer level.
The amplifier feedback resistors are internally connected to
V
OUT
on the AD7847.
The AD7837/AD7847 is fabricated in Linear Compatible CMOS
(LC
2
MOS), an advanced, mixed technology process that com-
bines precision bipolar circuits with low power CMOS logic.
A novel low leakage configuration (U.S. Patent No. 4,590,456)
ensures low offset errors over the specified temperature range.
DGND
V
SS
V
DD
AD7847
V
REFA
V
REFB
DB0
DB11
WR
CSA
CSB
CONTROL
LOGIC
DAC LATCH A
DAC A
V
OUTA
AGNDA
DAC B
V
OUTB
AGNDB
DAC LATCH B
DGND
V
SS
PRODUCT HIGHLIGHTS
1. The AD7837/AD7847 is a dual, 12-bit, voltage-out MDAC
on a single chip. This single chip design offers considerable
space saving and increased reliability over multichip designs.
2. The AD7837 and the AD7847 provide a fast versatile inter-
face to 8-bit or 16-bit data bus structures.
REV. C
Information furnished by Analog Devices is believed to be accurate and
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
AD [ ANALOG DEVICES ]
