AD7302

–11–

REV. 0

is the voltage applied to the external REFIN pin when

internal reference is used.

Table I. Output Voltage for Selected Input Codes

Digital Input

MSB . . . LSB

Analog Output

1111 1111

2

× 255/256 × V

1111 1110

2

× 254/256 × V

1000 0001

2

× 129/256 × V

1000 0000

0111 1111

2

× 127/256 × V

0000 0001

2

× V

0000 0000

0 V

00

01

DAC INPUT

CODE

FF

80

81

FE

7F

0

Figure 26. DAC Transfer Function

Figure 27 shows a typical setup for the AD7302 when using its

internal reference. The internal reference is selected by tying the

on the voltage connected to the REFIN pin. If REFIN is within

a threshold voltage of a PMOS device (approximately 1 V) of

this pin is used as the reference for the DAC. The internal

converter within the AD7302 provides a gain of two. Thus the

AD7302

10µF

0.1µF

A/B

REF IN

CLR

PD

AGND DGND

CS

WR LDAC

D7–D0

DATA BUS

CONTROL INPUTS

Figure 27. Typical Configuration Selecting the Internal

Reference

Figure 28 shows a typical setup for the AD7302 when using an

external reference. The reference range for the AD7302 is from

but will saturate the output at both the top and bottom end of

the transfer function. There is a gain of two from input to output

on the AD7302. Suitable references for 5 V operation are the

AD780 and REF192. For 3 V operation a suitable external

reference would be the AD589 a 1.23 V bandgap reference.

AD7302

10µF

0.1µF

AD780/REF192

OR

REF IN

GND

0.1µF

EXT REF

AGND DGND

D7–D0

DATA BUS

CONTROL INPUTS

A/B

CLR

PD

CS

WR LDAC

Figure 28. Typical Configuration Using An External

Reference