Rainbow Electronics MAX5153 - Manual (Page 16)

MAX5152/MAX5153
Digital Programmable Current Source
Figure 15 depicts a digitally programmable, unidirec-
tional current source that can be used in industrial con-
trol applications. The output current is:
I OUT = (V REF / R) (NB / 8192)
where NB is the DAC code and R is the sense resistor.
Power-Supply Considerations
On power-up, the input and DAC registers clear (reset
to zero code). For rated performance, V
REF_ should be
at least 1.4V below V DD . Bypass the power supply with
a 4.7µF capacitor in parallel with a 0.1µF capacitor to
GND. Minimize lead lengths to reduce lead inductance.
Grounding and Layout Considerations
Digital and AC transient signals on AGND can create
noise at the output. Connect AGND to the highest quali-
ty ground available. Use proper grounding techniques,
such as a multilayer board with an unbroken, low-
inductance ground plane. Carefully lay out the traces
between channels to reduce AC cross-coupling and
crosstalk. Wire-wrapped boards and sockets are not
recommended. If noise becomes an issue, shielding
may be required.
Low-Power, Dual, 13-Bit Voltage-Output DACs
with Configurable Outputs
16 ______________________________________________________________________________________
MAX5152
MAX5153
DAC_
REF_
2N3904
R
V L
I OUT
AGND
FB_
OUT_
+5V/+3V
V
DD
DGND
Figure 15. Digitally Programmable Current Source