max5230beeet Maxim Integrated Products, Inc., max5230beeet Datasheet - Page 15

• Manufacturer Part Number: max5230beeet
• Description: 3v/5v, 12-bit, Serial Voltage-output Dual Dacs With Internal Reference
• Manufacturer: Maxim Integrated Products, Inc.

Table 4. Unipolar Code Table
Digital feedthrough is noise generated on the DAC’s
output when any digital input transitions. Proper board
layout and grounding significantly reduce this noise,
but there is always some feedthrough caused by the
DAC itself.
Figure 7 shows the MAX5230/MAX5231 configured for
unipolar, rail-to-rail operation. The MAX5231 produces
a 0 to 4.095V output, while the MAX5230 produces 0 to
2.0475V output. Table 4 lists the unipolar output codes.
Figure 7. Unipolar Output Circuit (Rail-to-Rail)
1111 1111 1
1000 0000 0
1000 0000 0
0111 1111 1
0000 0000
0000 0000 0
3V/5V, 12-Bit, Serial Voltage-Output Dual DACs
MSB
DAC CONTENTS
GAIN = 1.6384V/V
111 (0)
001 (0)
000 (0)
111 (0)
001 (0)
000 (0)
REF
LSB
MAX5230
MAX5231
DAC_
______________________________________________________________________________________
AGND
REF
MAX5230
5V/3V
DGND
2.04750
1.02425
1.02375
1.02325
0.00050
V
ANALOG OUTPUT (V)
DD
0
Digital Feedthrough
Unipolar Output
121kΩ
77.25kΩ
1kΩ
MAX5231
OS_
4.0950
2.0485
2.0475
2.0465
0.0010
OUT_
0
with Internal Reference
Figure 8 shows the MAX5230/MAX5231 in a digital cali-
bration application. With a bright light value applied to
the photodiode (on), the DAC is digitally ramped until it
trips the comparator. The microprocessor (µP) stores
this “high” calibration value. Repeat the process with a
dim light (off) to obtain the dark current calibration. The
µP then programs the DAC to set an output voltage at
the midpoint of the two calibrated values. Applications
include tachometers, motion sensing, automatic read-
ers, and liquid clarity analysis.
Several MAX5230/MAX5231s may share one common
DIN signal line (Figure 9). In this configuration, the data
bus is common to all devices; data is not shifted through
a daisy-chain. The SCLK and DIN lines are shared by all
devices, but each IC needs its own dedicated CS line.
Any number of MAX5230/MAX5231s can be daisy-
chained by connecting the serial data output (DOUT) of
one device to the digital input (DIN) of the following
device in the chain (Figure 10).
Figure 8. Digital Calibration
REF
MAX5230
MAX5231
DAC_
AGND
REF
DGND
Sharing a Common DIN Line
5V/3V
V
DD
Daisy-Chaining Devices
Digital Calibration and
121kΩ
77.25kΩ
1kΩ
Threshold Selection
OUT_
OS_
V+
R
PHOTODIODE
PULLDOWN
V+
V-
V
OUT
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