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MAX5253A Datasheet - Page 14

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+3V, Quad, 12-Bit Voltage-Output DAC
with Serial Interface
+3.3V
REFERENCE INPUTS
MAX5253
REFAB
V
REFCD
DD
DAC A
DAC B
DAC C
DAC D
AGND
DGND
V
= V
= 1.25V
REFAB
REFCD
Figure 10. Unipolar Rail-to-Rail Output Circuit
R1
REF_
FB_
DAC
OUT_
MAX5253
R1 = R2 = 10kΩ ± 0.1%
Figure 11. Bipolar Output Circuit
14
______________________________________________________________________________________
In applications where the reference has AC signal com-
ponents, the MAX5253 has multiplying capability within
the reference input range specifications. Figure 12
shows a technique for applying a sine-wave signal to
10kΩ
FBA
the reference input where the AC signal is offset before
being applied to REFAB/REFCD. The reference voltage
16kΩ
must never be more negative than DGND.
OUTA
The MAX5253’s total harmonic distortion plus noise
10kΩ
FBB
(THD + N) is typically less than -72dB, given a 1V sig-
16kΩ
nal swing and input frequencies up to 25kHz. The typi-
cal -3dB frequency is 650kHz, as shown in the Typical
OUTB
Operating Characteristics graphs.
10kΩ
FBC
Digitally Programmable Current Source
16kΩ
The circuit of Figure 13 places an NPN transistor
(2N3904 or similar) within the op-amp feedback loop to
OUTC
10kΩ
FBD
implement a digitally programmable, unidirectional cur-
rent source. This circuit can be used to drive 4mA to
16kΩ
20mA current loops, which are commonly used in
industrial-control applications. The output current is cal-
OUTD
culated with the following equation:
where NB is the numeric value of the DAC’s binary
input code and R is the sense resistor shown in
Figure 13.
+3.3V
AC
26kΩ
REFERENCE
INPUT
R2
500mV
P-P
+5V
V
OUT
-5V
Figure 12. AC Reference Input Circuit
Using an AC Reference
I
= (V
/ R) x (NB / 4096)
OUT
REF
1/2 MAX492
10kΩ
V
REF_
DD
DAC_
MAX5253
AGND
DGND
OUT_

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