Bipolar Output

The MAX5150/MAX5151 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 MAX5150/MAX5151 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 REF.

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 MAX5150/MAX5151 in a digital

calibration application. With a bright light value applied

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

it trips the comparator. The microprocessor stores this

“high” calibration value. Repeat the process with a

dim light (off) to obtain the dark current calibration.

Low-Power, Dual, 13-Bit Voltage-Output DACs

with Serial Interface

14

______________________________________________________________________________________

Table 3. Bipolar Code Table

ANALOG OUTPUT

11111

1111

1111

10000

0000

0001

DAC CONTENTS

MSB

LSB

10000

0000

0000

0V

01111

1111

1111

00000

0000

0000

00000

0000

0001

+V

4095

4096

REF









+V

1

4096

REF









-V

1

4096

REF









-V

4095

4096

REF









-V

4096

4096

- V

REF

REF









=

AGND

DGND

R

R

TOLERANCES: 10k

Ω ± 0.1%

MAX5150

MAX5151

DAC _

REF_

OS_

OUT_

10k

10k

10k

10k

V-

V+

+5V/+3V

Figure 11. Bipolar Output Circuit

DAC_

OUT

MAX5150

MAX5151

10k

26k

OS_

REF

R

R

GND

AGND

+5V/

+3V

AC

REFERENCE

INPUT

500mVp-p

MAX495

+5V/+3V

Figure 12. AC Reference Input Circuit

AGND

DIN

µP

DGND

MAX5150

MAX5151

DAC _

REF_

OS_

OUT_

R

R

V-

V+

PHOTODIODE

V+

+5V/+3V

Figure 13. Digital Calibration