Quad, Serial 8-Bit DACs

with Rail-to-Rail Outputs

______________________________________________________________________________________

15

Unipolar-Output, 2-Quadrant Multiplication

In unipolar operation, the output voltages and the refer-

ence input(s) are the same polarity. Figures 11 and 12

show the MAX509/MAX510 unipolar configurations.

Both devices can be operated from a single supply if

the reference inputs are positive. If dual supplies are

Table 2 shows the unipolar code.

Bipolar-Output, 2-Quadrant Multiplication

Bipolar-output, 2-quadrant multiplication is achieved by

offsetting AGND positively or negatively. Table 3 shows

the bipolar code.

AGND can be biased above DGND to provide an arbi-

trary nonzero output voltage for a 0 input code, as

shown in Figure 13. The output voltage at OUTA is:

Figure 9. Suggested MAX509 PC Board Layout for Minimizing

Crosstalk (Bottom View)

OUTC

OUTD

REFC

REFD

OUTB

OUTA

REFB

REFA

SYSTEM GND

AGND

Figure 10. Suggested MAX510 PC Board Layout for Minimizing

Crosstalk (Bottom View)

OUTC

OUTD

REFCD

OUTB

OUTA

REFAB

SYSTEM GND

AGND

DAC CONTENTS

MSB

LSB

ANALOG

OUTPUT

1 1 1 1

1 1 1 1

255

256

1 0 0 0

0 0 0 1

129

256

1 0 0 0

0 0 0 0

128

256

2

0 1 1 1

1 1 1 1

127

256

0 0 0 0

0 0 0 0

0V

0 0 0 0

0 0 0 1

1

256

Table 2. Unipolar Code Table

1

256

Table 3. Bipolar Code Table

1 0 0 0

DAC CONTENTS

0 0 0 1

MSB

LSB

ANALOG

OUTPUT

1 1 1 1

1 1 1 1

127

128

1

128

1 0 0 0

0 0 0 0

0V

0 1 1 1

1 1 1 1

1

128

0 0 0 0

0 0 0 0

128

128

0 0 0 0

0 0 0 1

127

128