MCP4018 MICROCHIP [Microchip Technology], MCP4018 Datasheet - Page 41

• Manufacturer Part Number: MCP4018
• Manufacturer: MICROCHIP [Microchip Technology]

6.0
The Resistor Network is made up of two parts. These
are:
• Resistor Ladder
• Wiper
Figure 6-1
network.
Digital potentiometer applications can be divided into
two resistor network categories:
• Rheostat configuration
• Potentiometer (or voltage divider) configuration
The MCP4017 is a true rheostat, with terminal B and
the wiper (W) of the variable resistor available on pins.
The MCP4018 device offers a voltage divider
(potentiometer) with terminal B internally connected to
ground.
The MCP4019 device is a Rheostat device with
terminal A of the resistor floating, terminal B internally
connected to ground, and the wiper (W) available on
pin.
6.1
The resistor ladder is a series of equal value resistors
(R
resistors. The total number of resistors in the series
(ladder) determines the R
1). The end points of the resistor ladder are connected
to the device Terminal A and Terminal B pins. The R
(and R
and temperature.
The Resistor Network has 127 resistors in a string
between terminal A and terminal B. This gives 7-bits of
resolution.
The wiper can be set to tap onto any of these 127
resistors
(including terminal A and terminal B). This allows zero
scale to full scale connections.
A wiper setting of 00h connects the Terminal W (wiper)
to Terminal B (Zero Scale). A wiper setting of 3Fh is the
Mid scale setting. A wiper setting of 7Fh connects the
Terminal W (wiper) to Terminal A (Full Scale).
1
Terminal A and B as well as the wiper W do not have a
polarity. These terminals can support both positive and
negative current.
© 2009 Microchip Technology Inc.
illustrates the full wiper setting map.
S
) with a connection point (tap) between the two
S
) resistance has small variations over voltage
RESISTOR NETWORK
Resistor Ladder Module
thus
shows a block diagram for the resistive
providing
AB
resistance (see
128
possible
Figure 6-
Table 6-
settings
AB
FIGURE 6-1:
Diagram.
TABLE 6-1:
Wiper Setting
Note 1: The wiper resistance is tap dependent.
07Eh - 040h
03Eh - 001h
R
R
R
R
S
S
S
S
07Fh
03Fh
000h
A
B
N = 127
N = 126
N = 125
N = 1
N = 0
That is, each tap selection resistance
has a small variation. This variation has
more effect on devices with smaller R
resistance (5.0 kΩ).
MCP4017/18/19
WIPER SETTING MAP
Properties
Full Scale (W = A)
W = N
W = N (Mid Scale)
W = N
Zero Scale (W = B)
RW
RW
RW
RW
RW
Resistor Network Block
(1)
(1)
(1)
(1)
(1)
7Eh
7Fh
7Dh
01h
00h
Analog
Mux
DS22147A-page 41
W
AB