AD7302

–13–

REV. 0

APPLICATIONS

Bipolar Operation Using the AD7302

The AD7302 has been designed for single supply operation,

but bipolar operation is achievable using the circuit shown in

Figure 32. The circuit shown has been configured to achieve an

at the amplifier output is achievable using an AD820 or OP295

as the output amplifier.

The output voltage for any input code can be calculated as

follows:

× (R2/(R1+R2) × (2 × V

REF

× D/256)] – R4 × V

where

D is the decimal equivalent of the code loaded to the DAC

and

Ω and R2 = R4 = 20 kΩ and

× D/256) – 5 V

AD7302

10µF

0.1µF

AGND

AD780/REF192

OR

REF IN

GND

0.1µF

EXT REF

R1

10k

Ω

R2

20k

Ω

R4

20k

Ω

R3

10k

Ω

+5V

–5V

±5V

DGND

AD820/

OP295

Figure 32. Bipolar Operation Using the AD7302

Decoding Multiple AD7302 in a System

The

CS pin on the AD7302 can be used in applications to

decode a number of DACs. In this application all DACs in the

system receive the same input data, but only the

CS to one of

the DACs will be active at any one time allowing access to two

channels in the system. The 74HC139 is used as a two-to-four

line decoder to address any of the DACs in the system. To

prevent timing errors from occurring, the enable input should

be brought to its inactive state while the coded address inputs are

changing state. Figure 33 shows a diagram of a typical setup for

decoding multiple AD7302 devices in a system. The built-in

power-on reset circuit on the AD7302 ensures that the outputs

of all DACs in the system power up with zero volts on their

outputs.

AD7302

D0

D8

ENABLE

74HC139

DATA BUS

DGND

CODED

ADDRESS

1A

1B

1Y0

1Y1

1Y2

1Y3

1

AD7302

D0

D8

AD7302

D0

D8

AD7302

D0

D8

Figure 33. Decoding Multiple AD7302 DACs in a System

AD7302 As a Digitally Programmable Window Detector

A digitally programmable upper/lower limit detector using the

two DACs in the AD7302 is shown in Figure 34. The upper

and lower limits for the test are loaded to DACs A and B, which

is not within the programmed window an LED will indicate the

fail condition.

AD7302

+5V

DGND

REFIN

PASS/FAIL

1/2 CMP04

1/6 74HC05

FAIL

PASS

1k

0.1µF

10µF

WR

CS

A/B

1k

LDAC

CLR

PD

AGND

D0

D7

Figure 34. Programmable Window Detector