Applications information – Rainbow Electronics MAX513 User Manual

Page 12

MAX512/MAX513

Low-Cost, Triple, 8-Bit Voltage-Output DACs
with Serial Interface

______________________________________________________________________________________

_____________

Applications Information

Power-Supply and Reference

Operating Ranges

The MAX512 is fully specified to operate with
V

= 5V ±10% and V

= GND = 0V. The MAX513 is

specified for single-supply operation with V

ranging from

2.7V to 3.6V, covering all commonly used supply voltages
in 3V systems. The MAX512/MAX513 can also be used
with a negative supply ranging from -1.5V to -5.5V. Using a
negative supply typically improves zero-code error and
settling time (as shown in the

Typical Operating

Characteristics graphs).

The two separate reference inputs for the DAC pair A/B
and the unbuffered output C allow different full-scale out-
put voltages and, if a negative supply is used, also allow
different polarity. In dual-supply mode, REFAB can vary
from V

to (V

- 1.5V). In single-supply mode, the

specified range for REFAB is 0V to V

. REFC can range

from GND to V

. Do not force REFC below ground.

Power-supply sequencing is not critical. If a negative sup-
ply is used, make sure V

is never more than 0.3V above

ground. Do not apply signals to the digital inputs until the
device is powered-up. If this is not possible, add current-
limiting resistors to the digital inputs.

Power-Supply Bypassing and

Ground Management

In single-supply operation (V

= GND), GND and V

should be connected to the highest quality ground
available. Bypass V

with a 0.1µF to 0.22µF capacitor

to GND. For dual-supply operation, bypass V

with a

0.1µF to 0.22µF capacitor to GND. Reference inputs
can be used without bypassing. For optimum line/load-
transient response and noise performance, bypass the
reference inputs with 0.1µF to 4.7µF to GND. Careful
PC board layout minimizes crosstalk among DAC out-
puts, reference inputs, and digital inputs. Separate ana-
log lines with ground traces between them. Make sure
that high-frequency digital lines are not routed in paral-
lel to analog lines.

Unipolar Output

With unipolar output, the output voltage and the refer-
ence voltage are the same polarity. The MAX512/
MAX513 can be used with a single supply if the refer-
ence voltages are positive. With a negative supply,
t h e

REFAB voltage can vary from V

approximately (V

- 1.5V), allowing two-quadrant mul-

tiplication.

SCLK

DIN

LOUT

CSS

CSPWH

CSH

Figure 3. MAX512/MAX513 Detailed Serial-Interface Timing Diagram