MCP4725 Microchip Technology, MCP4725 Datasheet - Page 29

• Manufacturer Part Number: MCP4725
• Description: 12-Bit Digital-to-Analog Converter
• Manufacturer: Microchip Technology

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8.5.2
Calibrating the threshold of a diode, transistor or
resistor may require a very small step size in the DAC
output voltage. These applications may require about
200 µV of step resolution within 0.8V of range.
One method of achieving this small step resolution is
using a voltage divider at the DAC output. An example
is shown in
EXAMPLE 8-1:
© 2007 Microchip Technology Inc.
Example
DECREASING THE OUTPUT STEP
SIZE
1
2
3
(Ceramic) (Tantalum)
V
V
V
0.1 µF
MCP4725
OUT
SS
DD
8-1. The step size of the DAC out-
SCL
SDA
A0
Set Point Or Threshold Calibration.
10 µF
6
5
4
V
DD
R R
V
DD
Light
R
1
R
R
2
SENSE
(MASTER)
To MCU
V
DD
V
0.1 µF
TRIP
put is scaled down by the factor of the ratio of the volt-
age divider. Note that the bypass capacitor on the
output of the voltage divider plays a critical function in
attenuating the output noise of the DAC and the
induced noise from the environment.
Comparator
D
V
V
TRIP
OUT
=
Input Code (0 to 4095)
=
=
V
V
DD
OUT
×
⎛
⎝
------------------ -
R
----------- -
4096
MCP4725
1
D
R
+
2
R
2
⎞
⎠
DS22039C-page 29