AD7393AN Analog Devices, AD7393AN Datasheet - Page 7

• Manufacturer Part Number: AD7393AN
• Description: +3 V/ Parallel Input Micropower 10- and 12-Bit DACs
• Manufacturer: Analog Devices

OPERATION
The AD7392 and AD7393 comprise a set of pin compatible,
12-bit/10-bit digital-to-analog converters. These single-supply
operation devices consume less than 100 microamps of current
while operating from power supplies in the +2.7 V to +5.5 V
range making them ideal for battery operated applications. They
contain a voltage-switched, 12-bit/10-bit, laser-trimmed digital-
to-analog converter, rail-to-rail output op amps, and a parallel-
input DAC register. The external reference input has constant
input resistance independent of the digital code setting of the
DAC. In addition, the reference input can be tied to the same
supply voltage as V
span of 0 to V
bits, DB0–DB11, for the AD7392; 10 data bits, DB0–DB9, for
the AD7393; and a CS write strobe. A RS pin is available to
reset the DAC register to zero scale. This function is useful for
power-on reset or system failure recovery to a known state.
Additional power savings are accomplished by activating the
SHDN pin, resulting in a 1.5 A maximum consumption sleep
mode. As long as the supply voltage remains, data will be re-
tained in the DAC register to reset the DAC output when the
part is taken out of shutdown (SHDN = 1).
REV. A
IDD ( A)
V
OUT
Figure 23. Shutdown Recovery Time
SHDN
DD
(V)
100
50
. The parallel data interface consists of 12 data
0
2
0
1
0
100
10
90
0%
DD
, resulting in a maximum output voltage
TIME – 100 s/DIV
CS
H
L
X
H
NOTE
Positive logic transition; X Don’t Care.
Table I. Control Logic Truth Table
RS
H
H
H
L
–7–
D/A CONVERTER SECTION
The voltage switched R-2R DAC generates an output voltage
dependent on the external reference voltage connected to the
REF pin according to the following equation:
where D is the decimal data word loaded into the DAC register,
and N is the number of bits of DAC resolution. In the case of
the 10-bit AD7393 using a 2.5 V reference, Equation 1 simpli-
fies to:
Using Equation 2, the nominal midscale voltage at V
for D = 512; full-scale voltage is 2.497 volts. The LSB step size is
= 2.5
For the 12-bit AD7392 operating from a 5.0 V reference Equa-
tion 1 becomes:
Using Equation 3, the AD7392 provides a nominal midscale
voltage of 2.50 V for D = 2048, and a full-scale output of 4.998
volts. The LSB step size is = 5.0 1/4096 = 0.0012 volts.
DAC Register Function
Latched
Transparent
Latched with New Data
Loaded with All Zeros
Latched all Zeros
Figure 24. Shutdown Current vs. Temperature
1/1024 = 0.0024 volts.
V
V
V
OUT
OUT
OUT
1000
100
10
–55 –35
V
V
2.5
REF
REF
AD7392
–15
1024
D
2
2
TEMPERATURE – C
D
D
N
N
5
25
AD7392/AD7393
45
65
SHDN = 0V
V
V
DD
REF
= 5.5V
85 105
= 2.5V
125
OUT
Equation 1
Equation 2
Equation 3
is 1.25 V