Microchip Technology MCP4018T-104E/LT Linear IC SC-70-6 MCP4018T-104E/LT Ficha De Dados
Códigos do produto
MCP4018T-104E/LT
© 2009 Microchip Technology Inc.
DS22147A-page 43
MCP4017/18/19
6.2
Resistor Configurations
6.2.1
RHEOSTAT CONFIGURATION
When used as a rheostat, two of the three digital
potentiometer’s terminals are used as a resistive
element in the circuit. With terminal W (wiper) and
either terminal A or terminal B, a variable resistor is
created. The resistance will depend on the tap setting
of the wiper (and the wiper’s resistance). The
resistance is controlled by changing the wiper setting
The unused terminal (B or A) should be left floating.
potentiometer’s terminals are used as a resistive
element in the circuit. With terminal W (wiper) and
either terminal A or terminal B, a variable resistor is
created. The resistance will depend on the tap setting
of the wiper (and the wiper’s resistance). The
resistance is controlled by changing the wiper setting
The unused terminal (B or A) should be left floating.
shows the two possible resistors that can be
used. Reversing the polarity of the A and B terminals
will not affect operation.
will not affect operation.
FIGURE 6-2:
Rheostat Configuration.
This allows the control of the total resistance between
the two nodes. The total resistance depends on the
“starting” terminal to the Wiper terminal. So at the code
00h, the R
the two nodes. The total resistance depends on the
“starting” terminal to the Wiper terminal. So at the code
00h, the R
BW
resistance is minimal (R
W
), but the R
AW
resistance in maximized (R
AB
+ R
W
). Conversely, at the
code 3Fh, the R
AW
resistance is minimal (R
W
), but the
R
BW
resistance in maximized (R
AB
+ R
W
).
The resistance Step size (R
S
) equates to one LSb of
the resistor.
The pinout for the rheostat devices is such that as the
wiper register is incremented, the resistance of the
resistor will increase (as measured from Terminal B to
the W Terminal).
wiper register is incremented, the resistance of the
resistor will increase (as measured from Terminal B to
the W Terminal).
6.2.2
POTENTIOMETER
CONFIGURATION
CONFIGURATION
When used as a potentiometer, all three terminals of
the device are tied to different nodes in the circuit. This
allows the potentiometer to output a voltage
proportional to the input voltage. This configuration is
sometimes called voltage divider mode. The
potentiometer is used to provide a variable voltage by
adjusting the wiper position between the two endpoints
as shown in
the device are tied to different nodes in the circuit. This
allows the potentiometer to output a voltage
proportional to the input voltage. This configuration is
sometimes called voltage divider mode. The
potentiometer is used to provide a variable voltage by
adjusting the wiper position between the two endpoints
as shown in
. Reversing the polarity of the A
and B terminals will not affect operation.
FIGURE 6-3:
Potentiometer
Configuration.
The temperature coefficient of the R
AB
resistors is
minimal by design. In this configuration, the resistors all
change uniformly, so minimal variation should be seen.
The Wiper resistor temperature coefficient is different
to the R
change uniformly, so minimal variation should be seen.
The Wiper resistor temperature coefficient is different
to the R
AB
temperature coefficient. The voltage at node
V3 (
) is not dependent on this Wiper
resistance, just the ratio of the R
AB
resistors, so this
temperature coefficient in most cases can be ignored.
Note:
To avoid damage to the internal wiper
circuitry in this configuration, care should
be taken to insure the current flow never
exceeds 2.5 mA.
circuitry in this configuration, care should
be taken to insure the current flow never
exceeds 2.5 mA.
A
B
W
Resistor
R
AW
R
BW
or
Note:
To avoid damage to the internal wiper
circuitry in this configuration, care should
be taken to insure the current flow never
exceeds 2.5 mA.
circuitry in this configuration, care should
be taken to insure the current flow never
exceeds 2.5 mA.
A
B
W
V
1
V
3
V
2