Bipolar Output

The MAX5154/MAX5155 can be configured for a bipo-

lar output, as shown in Figure 11. The output voltage is

given by the equation (OS_ = AGND):

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 MAX5154/MAX5155 have multiplying

capabilities within the reference input voltage range

specifications. Figure 12 shows a technique for apply-

ing 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. The typical -3dB frequency is 300kHz

for both devices, as shown in the

Typical Operating

Characteristics.

Digital Calibration and

Threshold Selection

Figure 13 shows the MAX5154/MAX5155 in a digital

calibration application. With a bright light value applied

to the photodiode (on), the DAC is digitally ramped until

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

with Serial Interface

14

______________________________________________________________________________________

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

2048

REF









-V

2048

2048

- V

REF

REF









=

AGND

DGND

R

R

MAX5154

MAX5155

DAC _

REF_

OS_

OUT_

10k

10k

10k

10k

V-

V+

+5V/+3V

Figure 11. Bipolar Output Circuit

DAC_

OUT_

MAX5154

MAX5155

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

MAX5154

MAX5155

DAC _

REF_

OS_

OUT_

R

R

V-

V+

PHOTODIODE

V+

+5V/+3V

Figure 13. Digital Calibration

Note: ( ) are for the sub bit.