REV. B
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a
LC
2
MOS Quad 8-Bit DAC
with Separate Reference Inputs
AD7225
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
FUNCTIONAL BLOCK DIAGRAM
GENERAL DESCRIPTION
The AD7225 contains four 8-bit voltage output digital-to-
analog converters, with output buffer amplifiers and interface
logic on a single monolithic chip. Each D/A converter has a
separate reference input terminal. No external trims are re-
quired to achieve full specified performance for the part.
The double-buffered interface logic consists of two 8-bit regis-
ters per channel–an input register and a DAC register. Control
inputs A0 and A1 determine which input register is loaded when
WR goes low. Only the data held in the DAC registers deter-
mines the analog outputs of the converters. The double-
buffering allows simultaneous update of all four outputs under
control of LDAC. All logic inputs are TTL and CMOS (5 V)
level compatible and the control logic is speed compatible with
most 8-bit microprocessors.
Specified performance is guaranteed for input reference voltages
from +2 V to +12.5 V when using dual supplies. The part is also
specified for single supply operation using a reference of +10 V.
Each output buffer amplifier is capable of developing +10 V
across a 2 kΩ load.
The AD7225 is fabricated on an all ion-implanted high-speed
Linear Compatible CMOS (LC
2
MOS) process which has been
specifically developed to integrate high speed digital logic cir-
cuits and precision analog circuitry on the same chip.
FEATURES
Four 8-Bit DACs with Output Amplifiers
Separate Reference Input for Each DAC
mP Compatible with Double-Buffered Inputs
Simultaneous Update of All Four Outputs
Operates with Single or Dual Supplies
Extended Temperature Range Operation
No User Trims Required
Skinny 24-Pin DIP, SOIC and 28-Terminal Surface
Mount Packages
PRODUCT HIGHLIGHTS
1. DACs and Amplifiers on CMOS Chip
The single-chip design of four 8-bit DACs and amplifiers al-
lows a dramatic reduction in board space requirements and
offers increased reliability in systems using multiple convert-
ers. Its pinout is aimed at optimizing board layout with all
analog inputs and outputs at one end of the package and all
digital inputs at the other.
2. Single or Dual Supply Operation
The voltage-mode configuration of the AD7225 allows single
supply operation. The part can also be operated with dual
supplies giving enhanced performance for some parameters.
3. Versatile Interface Logic
The AD7225 has a common 8-bit data bus with individual
DAC latches, providing a versatile control architecture for
simple interface to microprocessors. The double-buffered in-
terface allows simultaneous update of the four outputs.
4. Separate Reference Input for Each DAC
The AD7225 offers great flexibility in dealing with input sig-
nals with a separate reference input provided for each DAC
and each reference having variable input voltage capability.