MCP4821T-E/P MICROCHIP [Microchip Technology], MCP4821T-E/P Datasheet - Page 25

• Manufacturer Part Number: MCP4821T-E/P
• Manufacturer: MICROCHIP [Microchip Technology]

6.9
Example 6-6 illustrates a variation on a voltage follower
design where a sense resistor is used to convert the
DAC’s voltage output into a digitally-selectable current
source.
Adding the resistor network from Example 6-2 would
be advantageous in this application. The smaller
R
However, this also reduces the resolution that the
current can be controlled with. The voltage divider, or
“window”, DAC configuration would allow the range to
be reduced, thus increasing resolution around the
range of interest. When working with very small sensor
voltages, plan on eliminating the amplifier's offset error
by storing the DAC's setting under known sensor
conditions.
EXAMPLE 6-6:
© 2005 Microchip Technology Inc.
SENSE
SPI™
G = Gain select (1x or 2x)
V
D = Digital value of DAC (0 – 4096)
OUT
I
I
Building A Programmable Current
Source
b
L
is, the less power dissipated across it.
MCP482X
3
=
=
=
V
I
----
2.048V G
-------------- -
R
DD
V
L
sense
OUT
----------- -
Digitally-Controlled Current
Source.
-------
2
+
V
D
12
OUT
1
V
V
CC
CC
–
R
+
sense
I
b
Load
I
L
MCP4821/MCP4822
DS21953A-page 25