Low-Power, Dual, Voltage-Output, 12-Bit DAC

with Serial Interface

______________________________________________________________________________________

11

where NB represents the numeric value of the DAC’s

binary input code. Table 3 shows digital codes and the

corresponding output voltage for Figure 11’s circuit.

Using an AC Reference

In applications where the reference has an AC signal

component, the MAX5104 has multiplying capabilities

within the reference input voltage range specifications.

Figure 12 shows a technique for applying a sinusoidal

input to REF_, where the AC signal is offset before

being applied to the reference input.

Harmonic Distortion and Noise

The total harmonic distortion plus noise (THD+N) is typ-

ically less than -78dB at full scale with a 1Vp-p input

swing at 5kHz.

Digital Calibration and

Threshold Selection

Figure 13 shows the MAX5104 in a digital calibration

application. With a bright-light value applied to the pho-

todiode (on), the DAC is digitally ramped until it trips

the comparator. The microprocessor (µP) stores this

“high” calibration value. Repeat the process with a dim

light (off) to obtain the dark current calibration.

Table 3. Bipolar Code Table

ANALOG OUTPUT

1111 1111 1 111 (0)

1000 0000 0 001 (0)

DAC CONTENTS

MSB

LSB

1000 0000 0 000 (0)

0V

0111 1111 1 111 (0)

0000 0000 0 000 (0)

0000 0000 0 001 (0)

+V

2047

2048

REF









+V

1

2048

REF









-V

1

2048

REF









+V

2047

4096

REF









-V

2048

2048

-V

REF

REF









=

AGND

DGND

R

R

MAX5104

DAC _

REF_

OS_

OUT_

10k

10k

10k

10k

V-

V+

+5V/+3V

Figure 11. Bipolar Output Circuit

DAC_

OUT_

MAX5104

10k

26k

OS_

REF

R

R

DGND

AGND

+5V/

+3V

AC

REFERENCE

INPUT

500mVp-p

MAX495

+5V/+3V

Figure 12. AC Reference Input Circuit

AGND

DIN

µP

DGND

MAX5104

DAC _

REF_

OS_

OUT_

R

R

V-

V+

PHOTODIODE

V+

+5V/+3V

Figure 13. Digital Calibration

Note: ( ) are for the sub-bit.