LC
2
MOS
16-Bit Voltage Output DAC
AD7846
Rev. G
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FEATURES
16-bit monotonicity over temperature
±2 LSBs integral linearity error
Microprocessor compatible with readback capability
Unipolar or bipolar output
Multiplying capability
Low power (100 mW typical)
FUNCTIONAL BLOCK DIAGRAM
A2
A1
A3
16
SEGMENT
SWITCH
MATRIX
R
R
R
12-BIT DAC
DAC LATCH
I/O LATCH
CONTROL
LOGIC
AD7846
R
21 4
7
8
9
6
5
23
22
25
24
R
V
REF–
V
REF+
V
SS
DGND
CLR
LDAC
R/W
CS
V
OUT
R
IN
DD
CC
4
12
12
DB15 DB0
08490-001
10 3 20
Figure 1.
GENERAL DESCRIPTION
The AD7846 is a 16-bit DAC constructed with the Analog Devices,
Inc., LC
2
MOS process. It has V
REF+
and V
REF−
reference inputs
and an on-chip output amplifier. These can be configured to
give a unipolar output range (0 V to +5 V, 0 V to +10 V) or
bipolar output ranges (±5 V, ±10 V).
The DAC uses a segmented architecture. The four MSBs in the
DAC latch select one of the segments in a 16-resistor string.
Both taps of the segment are buffered by amplifiers and fed to a
12-bit DAC, which provides a further 12 bits of resolution. This
architecture ensures 16-bit monotonicity. Excellent integral
linearity results from tight matching between the input offset
voltages of the two buffer amplifiers.
In addition to the excellent accuracy specifications, the AD7846
also offers a comprehensive microprocessor interface. There are
16 data I/O pins, plus control lines (
CS
, R/
W
,
LDAC
and
CLR
).
R/
W
and
CS
allow writing to and reading from the I/O latch.
This is the readback function, which is useful in ATE applications.
LDAC
allows simultaneous updating of DACs in a multi-DAC
system and the
CLR
line will reset the contents of the DAC latch
to 00…000 or 10…000 depending on the state of R/
W
. This
means that the DAC output can be reset to 0 V in both the
unipolar and bipolar configurations.
The AD7846 is available in 28-lead plastic, ceramic, and PLCC
packages.
PRODUCT HIGHLIGHTS
1. 16-Bit Monotonicity
The guaranteed 16-bit monotonicity over temperature
makes the AD7846 ideal for closed-loop applications.
2. Readback
The ability to read back the DAC register contents
minimizes software routines when the AD7846 is used in
ATE systems.
3. Power Dissipation
Power dissipation of 100 mW makes the AD7846 the
lowest power, high accuracy DAC on the market.
