MCP4562 View Datasheet(PDF) - Microchip Technology
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MCP4562 Datasheet PDF : 66 Pages
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6.0 RESISTOR NETWORK
The Resistor Network is made up of two parts. These
are:
• Resistor Ladder
• Wiper
Figure 6-1 shows a block diagram for the resistive
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 Resistor Ladder Module
The resistor ladder is a series of equal value resistors
(RS) with a connection point (tap) between the two
resistors. The total number of resistors in the series
(ladder) determines the RAB resistance (see Figure 6-
1). The end points of the resistor ladder are connected
to the device Terminal A and Terminal B pins. The RAB
(and RS) resistance has small variations over voltage
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 thus providing 128 possible settings
(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). Table 6-
1 illustrates the full wiper setting map.
Terminal A and B as well as the wiper W do not have a
polarity. These terminals can support both positive and
negative current.
MCP4017/18/19
A
N = 127
7Fh
RW (1)
RS
N = 126
7Eh
RS
RW (1)
N = 125
7Dh
RS
RW (1)
W
N=1
RS
N=0
B
01h
RW (1)
00h
RW (1)
Analog
Mux
Note 1: The wiper resistance is tap dependent.
That is, each tap selection resistance
has a small variation. This variation has
more effect on devices with smaller RAB
resistance (5.0 kΩ).
FIGURE 6-1:
Diagram.
Resistor Network Block
TABLE 6-1: WIPER SETTING MAP
Wiper Setting Properties
07Fh
07Eh - 040h
03Fh
03Eh - 001h
000h
Full Scale (W = A)
W=N
W = N (Mid Scale)
W=N
Zero Scale (W = B)
© 2009 Microchip Technology Inc.
DS22147A-page 41
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