MAX5250 Maxim, MAX5250 Datasheet - Page 14

• Manufacturer Part Number: MAX5250
• Description: Low-Power / Quad / 10-Bit Voltage-Output DAC with Serial Interface
• Manufacturer: Maxim

Low-Power, Quad, 10-Bit Voltage-Output DAC
with Serial Interface
Figure 10. Unipolar Rail-to-Rail Output Circuit
Figure 11. Bipolar Output Circuit
14
V
MAX5250
REFAB
REF_
______________________________________________________________________________________
DAC
= V
REFCD
REFAB
= 2.5V
MAX5250
REFERENCE INPUTS
DAC A
DAC B
DAC C
DAC D
R1
REFCD
AGND
OUT_
FB_
R1 = R2 = 10k ± 0.1%
V
DD
+5V
DGND
+5V
-5V
R2
FBA
FBB
FBC
FBD
OUTA
OUTB
OUTC
OUTD
10k
10k
10k
10k
10k
10k
10k
10k
V
OUT
In applications where the reference has AC signal com-
ponents, the MAX5250 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 MAX5250’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.
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:
where NB is the numeric value of the DAC’s binary
input code and R is the sense resistor shown in
Figure 13.
Figure 12. AC Reference Input Circuit
REFERENCE
500mVp-p
INPUT
+5V
AC
Digitally Programmable Current Source
26k
I
OUT
10k
= (V
REF
Using an AC Reference
DAC_
/ R) x (NB / 1024)
1/2 MAX492
REF_
AGND
MAX5250
V
DD
DGND
OUT_