Quad/Octal, 2-Wire Serial 8-Bit DACs

with Rail-to-Rail Outputs

16

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__________Applications Information

Shutdown Mode

In shutdown mode, the MAX520/MAX521 reference

inputs are disconnected from the R-2R ladder inputs,

which saves power when the reference is not powered

down. In addition, the MAX521’s output buffers are dis-

abled, greatly reducing the supply current. The

MAX520’s operating supply current does not change in

shutdown mode. The

Command Byte and Output Byte

section describes how to enter and exit shutdown

mode.

Power-Supply Bypassing and

Ground Management

(AGND) and digital ground (DGND) pins should be

connected in a “star” configuration to the highest quali-

ty ground available, which should be located as close

to the MAX521 as possible.

Careful PC board layout minimizes crosstalk among

DAC outputs, reference inputs, and digital inputs.

Figure 16 shows the suggested PC board layout to mini-

mize crosstalk.

OUT2

OUT3

REF2

REF3

OUT1

PIN1

OUT0

REF1

REF0

SYSTEM GND

Figure 16. PC Board Layout for Minimizing Crosstalk (MAX521

bottom view, DIP package)

(1%)

DAC

Figure 15a. Typical Trimming Circuit

(1%)

16k

Ω

DAC

MAX520A

Figure 15b. MAX520A Trimming Circuit