Rainbow Electronics MAX5251 - Manual (Page 13)

MAX5251
+3V, Quad, 10-Bit Voltage-Output DAC
with Serial Interface
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__________Applications Information
Unipolar Output
For a unipolar output, the output voltages and the refer-
ence inputs have the same polarity. Figure 9 shows the
MAX5251 unipolar output circuit, which is also the typi-
cal operating circuit. Table 2 lists the unipolar output
codes.
For rail-to-rail outputs, see Figure 10. This circuit shows
the MAX5251 with the output amplifiers configured with
a closed-loop gain of +2.6 to provide 0V to 3.25V full-
scale range when a 1.25V reference is used.
Bipolar Output
The MAX5251 outputs can be configured for bipolar
operation using Figure 11’s circuit:
V OUT = V REF [(2NB / 1024) - 1]
where NB is the numeric value of the DAC’s binary
input code. Table 3 shows digital codes (offset binary)
and corresponding output voltages for Figure 11’s
circuit.
Table 2. Unipolar Code Table
Table 3. Bipolar Code Table
DAC CONTENTS
ANALOG OUTPUT
MSB LSB
1023
1 1 1 1 1 1 1 1 1 1 ( 0 0 ) +V REF
(
———
)
1024
513
1000 0000 01(00) +V REF
(
———
)
1024
512 +V REF
1 0 0 0 0 0 0 0 0 0 ( 0 0 ) +V REF
(
———
)
= ————
1024 2
511
0 1 1 1 1 1 1 1 1 1 ( 0 0 ) +V REF
(
———
)
1024
1
0 0 0 0 0 0 0 0 0 1 ( 0 0 ) +V REF
(
———
)
1024
0 0 0 0 0 0 0 0 0 0 ( 0 0 ) 0V
DAC CONTENTS
ANALOG OUTPUT
MSB LSB
511
1 1 1 1 1 1 1 1 1 1 ( 0 0 ) +V REF
(
———
)
512
1
1000 0000 01(00) +V REF
(
———
)
512
1 0 0 0 0 0 0 0 0 0 ( 0 0 ) 0V
1
0 1 1 1 1 1 1 1 1 1 ( 0 0 ) -V REF
(
———
)
512
511
0 0 0 0 0 0 0 0 0 1 ( 0 0 ) -V REF
(
———
)
512
512
0 0 0 0 0 0 0 0 0 0 ( 0 0 ) -V REF
(
———
)
= -V REF
512
MAX5251
DAC A
DAC B
DAC C
DAC D
OUTA
FBA
FBB
FBC
FBD
OUTB
OUTC
OUTD
DGND AGND
REFAB REFCD
REFERENCE INPUTS
+3.3V
V DD
Figure 9. Unipolar Output Circuit
( ) Sub-bits