MAX509 Datasheet, PDF (15/20 Pages) Maxim Integrated Products – Quad, Serial 8-Bit DACs with Rail-to-Rail Outputs

OUTC
OUTD
V_DD
REFC
REFD
SYSTEM GND
Quad, Serial 8-Bit DACs
with Rail-to-Rail Outputs
OUTB
OUTA
V_SS
REFB
REFA
AGND
OUTC
OUTD
V_DD
REFCD
SYSTEM GND
OUTB
OUTA
V_SS
REFAB
AGND
Figure 9. Suggested MAX509 PC Board Layout for Minimizing
Crosstalk (Bottom View)
Unipolar-Output, 2-Quadrant Multiplication
In unipolar operation, the output voltages and the refer-
ence input(s) are the same polarity. Figures 11 and 12
show the MAX509/MAX510 unipolar configurations.
Both devices can be operated from a single supply if
the reference inputs are positive. If dual supplies are
used, the reference input can vary from VSS to VDD.
Table 2 shows the unipolar code.
Table 2. Unipolar Code Table
DAC CONTENTS
MSB
LSB
1111
1111
1000
0001
1000
0000
0111
1111
0000
0000
0001
0000
ANALOG
OUTPUT
( ) +V_REF
–2–5–5–
256
( ) +V_REF
–1–2–9–
256
( ) +V_REF
–1–2–8–
256
= +V–^{R–E–F–}
2
( ) ¹²⁷
+V_REF
––––
256
( ) +V_REF
––1––
256
0V
Note:
1LSB
=
(V_REF)
(2-8)
=
+V_REF
(––1––)
256
Figure 10. Suggested MAX510 PC Board Layout for Minimizing
Crosstalk (Bottom View)
Bipolar-Output, 2-Quadrant Multiplication
Bipolar-output, 2-quadrant multiplication is achieved by
offsetting AGND positively or negatively. Table 3 shows
the bipolar code.
AGND can be biased above DGND to provide an arbi-
trary nonzero output voltage for a 0 input code, as
shown in Figure 13. The output voltage at OUTA is:
VOUTA = V_BIAS + (NB/256)(VIN),
Table 3. Bipolar Code Table
DAC CONTENTS
MSB
LSB
ANALOG
OUTPUT
1111
1111
( ) +V_REF
1––2–7–
128
1000
1000
0001
0000
( ) +V_REF
––1––
128
0V
0111
1111
( ) -V_REF
––1––
128
0000
0001
( ) -V_REF
–1–2–7–
128
0000
0000
( ) -V_REF
–1–2–8–
128
= -V_REF
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