MAX5251ACAP 데이터 시트보기 (PDF) - Maxim Integrated
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MAX5251ACAP Datasheet PDF : 16 Pages
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+3V, Quad, 10-Bit Voltage-Output DAC
with Serial Interface
MAX5251
REFERENCE INPUTS
REFAB
REFCD
+3.3V
VDD
DAC A
DAC B
DAC C
DAC D
VREFAB = VREFCD = 1.25V
AV = 1 +
16k
10k
= 2.6
AGND
DGND
FBA 10k
16k
OUTA
FBB 10k
16k
OUTB
FBC 10k
16k
OUTC
FBD 10k
16k
OUTD
Figure 10. Unipolar Rail-to-Rail Output Circuit
Using an AC Reference
In applications where the reference has AC signal com-
ponents, the MAX5251 has multiplying capability within
the reference input range specifications. Figure 12
shows a technique for applying a sine-wave signal to
the reference input where the AC signal is offset before
being applied to REFAB/REFCD. The reference voltage
must never be more negative than DGND.
The MAX5251’s total harmonic distortion plus noise
(THD + N) is typically less than -72dB (full-scale code),
given a 1Vp-p signal swing and input frequencies up to
25kHz. The typical -3dB frequency is 650kHz, as
shown in the Typical Operating Characteristics graphs.
Digitally Programmable Current Source
The circuit of Figure 13 places an NPN transistor
(2N3904 or similar) within the op-amp feedback loop to
implement a digitally programmable, unidirectional cur-
rent source. This circuit can be used to drive 4–20mA
current loops, which are commonly used in industrial-
control applications. The output current is calculated
with the following equation:
IOUT = (VREF / R) x (NB / 1024)
where NB is the numeric value of the DAC’s binary
input code and R is the sense resistor shown in
Figure 13.
R1
R2
REF_
+3.3V
FB_
DAC
MAX5251
OUT_
-3.3V
R1 = R2 = 10kΩ ± 0.1%
+3.3V
AC
26k
REFERENCE
INPUT
500mVp-p
10k
VOUT
1/2 MAX492
REF_
VDD
DAC_
OUT_
MAX5251
AGND
DGND
Figure 11. Bipolar Output Circuit
Figure 12. AC Reference Input Circuit
14 ______________________________________________________________________________________
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