AD7392/AD7393

–7–

REV. A

TIME – 100 s/DIV

100

50

0

2

0

1

0

IDD ( A)

SHDN

100

90

0%

10

Figure 23. Shutdown Recovery Time

Table I. Control Logic Truth Table

CS

RS

DAC Register Function

H

H

Latched

L

H

Transparent

↑

H

Latched with New Data

X

L

Loaded with All Zeros

H

↑

Latched all Zeros

NOTE

↑ Positive logic transition; X Don’t Care.

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

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

µA 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).

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:

D

Equation 1

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:

D

1024

Equation 2

for D = 512; full-scale voltage is 2.497 volts. The LSB step size is

= 2.5

× 1/1024 = 0.0024 volts.

For the 12-bit AD7392 operating from a 5.0 V reference Equa-

tion 1 becomes:

D

Equation 3

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.

TEMPERATURE – C

1000

10

–55 –35

125

–15

65

85

105

525

45

100

SHDN = 0V

AD7392

Figure 24. Shutdown Current vs. Temperature