LC2MOS
12-Bit DACPORTs
a
AD7245A/AD7248A
FEATURES
AD7245A FUNCTIONAL BLOCK DIAGRAM
12-Bit CMOS DAC with Output Amplifier and
Reference
Improved AD7245/AD7248:
V
R
OFS
DD
REF OUT
2R
2R
R
FB
12 V to 15 V Operation
؎1/2 LSB Linearity Grade
V
OUT
Faster Interface—30 ns Typ Data Setup Time
Extended Plastic Temperature Range (–40؇C to +85؇C)
Single or Dual Supply Operation
Low Power—65 mW Typ in Single Supply
Parallel Loading Structure: AD7245A
(8+4) Loading Structure: AD7248A
V
REF
DAC
V
SS
AGND
CS
WR
DAC LATCH
INPUT LATCH
DB0 DB11
CLR
CONTROL
LOGIC
AD7245A
GENERAL DESCRIPTION
LDAC
The AD7245A/AD7248A is an enhanced version of the industry
standard AD7245/AD7248. Improvements include operation
from 12 V to 15 V supplies, a 1/2 LSB linearity grade, faster
interface times and better full scale and reference variations with
VDD. Additional features include extended temperature range
operation for commercial and industrial grades.
DGND
AD7248A FUNCTIONAL BLOCK DIAGRAM
The AD7245A/AD7248A is a complete, 12-bit, voltage output,
digital-to-analog converter with output amplifier and Zener voltage
reference on a monolithic CMOS chip. No external user trims
are required to achieve full specified performance.
V
R
OFS
DD
REF OUT
2R
2R
R
FB
Both parts are microprocessor compatible, with high speed data
latches and double-buffered interface logic. The AD7245A accepts
12-bit parallel data that is loaded into the input latch on the
rising edge of CS or WR. The AD7248A has an 8-bit-wide data
bus with data loaded to the input latch in two write operations.
For both parts, an asynchronous LDAC signal transfers data
from the input latch to the DAC latch and updates the analog
output. The AD7245A also has a CLR signal on the DAC latch
which allows features such as power-on reset to be implemented.
V
OUT
V
REF
DAC
V
SS
AGND
LDAC
DAC LATCH
WR
CONTROL
LOGIC
AD7248A
CSLSB
4-BIT
8-BIT
INPUT
LATCH
INPUT
CSMSB
LATCH
The on-chip 5 V buried Zener diode provides a low noise, tem-
perature compensated reference for the DAC. 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 available with dual supplies. The output amplifiers are capa-
ble of developing 10 V across a 2 kΩ load to GND.
DB7 DB0
DGND
PRODUCT HIGHLIGHTS
1. The AD7245A/AD7248A is a 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.
The AD7245A/AD7248A is fabricated in linear compatible CMOS
(LC2MOS), an advanced, mixed technology process that combines
precision bipolar circuits with low power CMOS logic. The
AD7245A is available in a small, 0.3" wide, 24-lead DIP and
SOIC and in 28-terminal surface mount packages. The AD7248A
is packaged in a small, 0.3" wide, 20-lead DIP and SOIC and in
20-terminal surface mount packages.
2. The improved interface times on the part allows easy, direct
interfacing to most modern microprocessors.
3. The AD7245A/AD7248A features a wide power supply range
allowing operation from 12 V supplies.
DACPORT is a registered trademark of Analog Devices, Inc.
REV. B
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
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 2001
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