MAX5302 Просмотр технического описания (PDF) - Maxim Integrated
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MAX5302 Datasheet PDF : 12 Pages
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Low-Power, 12-Bit Voltage-Output DAC
with Serial Interface
REF
MAX5302
DAC
+5V
VDD
GND
FB 10k
10k
OUT
REF
DAC
R1
+5V
VDD
FB
OUT
MAX5302
GND
R2
V+
VOUT
V-
R1 = R2 = 10kΩ ±0.1%
Figure 9. Unipolar Rail-to-Rail Output Circuit
Digitally Programmable Current Source
The circuit of Figure 12 places an NPN transistor (2N3904
or similar) within the op amp feedback loop to implement
a digitally programmable, unidirectional current source.
The output current is calculated with the following
equation:
IOUT = (VREF / R) (NB / 4096)
where NB is the numeric value of the DAC’s binary input
code, and R is the sense resistor shown in Figure 12.
Power-Supply Considerations
On power-up, the input and DAC registers are cleared
(set to zero code).
For rated MAX5302 performance, VREF must be at least
1.4V below VDD. Bypass VDD with a 4.7µF capacitor in
parallel with a 0.1µF capacitor to GND. Use short lead
lengths and place the bypass capacitors as close to
the supply pins as possible.
Grounding and Layout Considerations
Digital or AC transient signals on GND can create noise
at the analog output. Connect GND to the highest-quality
ground available.
Good PC board ground layout minimizes crosstalk
between the DAC output, reference input, and digital
input. Reduce crosstalk by keeping analog lines away
from digital lines. Wire-wrapped boards are not recom-
mended.
Figure 10. Bipolar Output Circuit
Table 3. Bipolar Code Table
DAC CONTENTS
MSB
LSB
ANALOG OUTPUT
1111 1111 1111 (0)
+VREF
2047
2048
1000 0000 0001 (0)
1000 0000 0000 (0)
+VREF
1
2048
0V
0111 1111 1111 (0)
0000 0000 0001 (0)
-VREF
1
2048
-VREF
2047
2048
0000 0000 0000 (0)
Note: ( ) are for sub-bit.
-VREF
2048
2048
= - VREF
10 ______________________________________________________________________________________
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