MAX520/MAX521
Quad/Octal, 2-Wire Serial 8-Bit DACs
with Rail-to-Rail Outputs
16 ______________________________________________________________________________________
__________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
Bypass V
DD
with a 0.1µF capacitor, located as close to
V
DD
and DGND as possible. The analog ground
(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%)
R
T
DAC
R
F
R
IN
Figure 15a. Typical Trimming Circuit
(1%)
16kΩ
DAC
R
F
R
IN
MAX520A
Figure 15b. MAX520A Trimming Circuit
