MCP41100 MICROCHIP [Microchip Technology], MCP41100 Datasheet - Page 16

• Manufacturer Part Number: MCP41100
• Manufacturer: MICROCHIP [Microchip Technology]

MCP41XXX/42XXX
FIGURE 4-7:
programmable differential amplifier using digital
potentiometers.
4.2.3
For applications requiring only a programmable voltage
reference, the circuit in Figure 4-8 can be used. This
circuit shows the device used in the potentiometer
mode along with two resistors and a buffered output.
This creates a circuit with a linear relationship between
voltage-out and programmed code. Resistors R
R
age step size. The potentiometer in this mode is stable
over temperature. The operation of this circuit over
temperature is shown in Figure 2-3. The worst perfor-
mance over temperature will occur at the lower codes
due to the dominating wiper resistance. R
also be used to affect the boundary voltages, thereby
eliminating the use of these lower codes.
FIGURE 4-8:
R
programmable voltage reference circuit is
affected.
DS11195C-page 16
2
1
(SIG +)
can be used to increase or decrease the output volt-
(SIG -)
and R
R
R
D
Where:
V
V
NOTE: Potentiometer values must be equal
A
AB
n
A
B
=
=
R
=
2
R
Wiper setting forD
R
-------------------------------------- -
2
MCP42010
, the voltage output resolution of this
PROGRAMMABLE OFFSET TRIM
1
A
B
Total Resistance of pot
A
AB
V
V
V
1/2
REF
DD
256 D
256
SS
A
B
B
+IN
-IN
–
+IN
0.1 uF
-IN
Single Supply
By changing the values of
+
-
n
MCP601
+
-
MCP606
V
R
V
n
V
OUT
V
SS
B
V
DD
=
SS
DD
=
0 to 255
=
R
----------------- -
OUT
256
AB
V
D
A
n
1
–
and R
V
B
V
R
------ -
R
OUT
1
B
A
2
and
can
4.3
When programming the digital potentiometer settings,
the following equations can be used to calculate the
resistances. Programming code 00h effectively brings
the wiper to the B terminal, leaving only the wiper resis-
tance. Programming higher codes will bring the wiper
closer to the A terminal of the potentiometer. The equa-
tions in Figure 4-9 can be used to calculate the terminal
resistances. Figure 4-10 shows an example calculation
using a 10 k potentiometer.
FIGURE 4-9:
are a function of code. It should be noted that,
when using these equations for most feedback
amplifier circuits (see Figure 4-4 and Figure 4-5),
the wiper resistance can be omitted due to the
high impedance input of the amplifier.
FIGURE 4-10:
calculations.
Where:
PA is the A terminal
PB is the B terminal
PW is the wiper terminal
R
R
R
R
D
WA
WB
AB
W
n
10 k
Note: All values shown are typical and
is 8-bit value in data register for pot number n
R
R
R
R
is wiper resistance
R
is overall resistance for pot (10 k , 50 k
is resistance between Terminal A and wiper
is resistance between Terminal B and Wiper
R
WA
WA
WB
WB
Calculating Resistances
WA
WB
R
R
WA
WB
actual results will vary.
C0h
C0h
C0h
C0h
D
D
n
n
D
D
n
n
=
=
=
=
=
=
------------------------------------------- -
=
=
PA
PW
PB
R
--------------------------- -
-------------------------------------------------- -
2552
---------------------------------- -
7552
R
10k
10k
Potentiometer resistances
Example Resistance
AB
------------------------------------------- -
--------------------------- -
AB
R
R
256
AB
AB
2003 Microchip Technology Inc.
256
256
256
256 D
D
256
256
256 192
n
192
256 D
D
Example:
R = 10 k
Code = C0h = 192d
–
n
PA
PW
PB
+
–
R
–
+
n
+
W
R
52
+
n
W
R
or 100 k )
+
W
+
R
52
W