www.ti.com

THEORY OF OPERATION

R

R

R

R

2R

2R

2R

2R

2R

DB0

(LSB)

DB9

DB10

DB11

(MSB)

I

1

OUT

R

FB

V

REF

I

2

OUT

R

1

V

OUT

CODE

4096

(1)

OPA277

15V

V+

V-

-15V

GND

I

1

OUT

R

FB

R /R

2

3

V

DD

V

DD

V

OUT

I

2

OUT

R

2

R

3

V

REF

R

1

DAC7822

DAC7822

SBAS374A – JUNE 2006 – REVISED JULY 2007

The DAC7822 is a dual channel, current output, 12-bit, digital-to-analog converter (DAC). The architecture,

illustrated in Figure 37, is an R-2R ladder configuration with the three MSBs segmented. Each 2R leg of the

potential by the use of an external I/V converter op amp. The R-2R ladder is connected to an external reference

impedance to the external reference of 10k

Ω ±20%. The external reference voltage can vary over a range of

Figure 37. Equivalent R-2R DAC Circuit

by Equation 1:

also changes. Because of this, the external I/V converter op amp must have a sufficiently low offset voltage such

large offset voltages can produce INL errors in the transfer function of the DAC7822 as a result of offset

modulation versus DAC code.

For best linearity performance of the DAC7822, a low input offset voltage op amp (such as the OPA277) is

Figure 38. Voltage Output Configuration

13

Submit Documentation Feedback