MCP4024 MICROCHIP [Microchip Technology], MCP4024 Datasheet - Page 44

• Manufacturer Part Number: MCP4024
• Manufacturer: MICROCHIP [Microchip Technology]

MCP4021/2/3/4
6.2
Wiper resistance is the series resistance of the wiper.
This resistance is typically measured when the wiper is
positioned at either zero-scale (00h) or full-scale (3Fh).
The wiper resistance in potentiometer-generated
voltage divider applications is not a significant source
of error.
The wiper resistance in rheostat applications can
create significant non-linearity as the wiper is moved
toward zero-scale (00h). The lower the nominal
resistance, the greater the possible error.
Wiper resistance is significant depending on the
devices operating voltage. As the device voltage
decreases, the wiper resistance increases (see
Figure 6-4
In a rheostat configuration, this change in voltage
needs to be taken into account, particularly for the
lower resistance devices. For the 2.1 kΩ device, the
maximum wiper resistance at 5.5V is approximately 6%
of the total resistance, while at 2.7V, it is approximately
15.5% of the total resistance.
In a potentiometer configuration, the wiper resistance
variation does not effect the output voltage seen on the
terminal W pin.
TABLE 6-2:
DS21945E-page 44
Note 1:
10000
50000
(R
Total
2100
5000
AB
Typical
)
2:
Wiper Resistance
and
158.73
793.65
R
R
33.33
79.37
Step
(R
S
AB
S
is the typical value. The variation of this resistance is minimal over voltage.
Table
Resistance (Ω)
)
is the typical value. The variation of this resistance is minimal over voltage.
TYPICAL STEP RESISTANCES AND RELATIONSHIP TO WIPER RESISTANCE
Typical
6-2).
75
75
75
75
Wiper (R
Max @
5.5V
125
125
125
125
W
)
Max @
2.7V
325
325
325
325
Typical
225.0%
47.25%
94.5%
9.45%
R
W
=
R
W
R
375.0%
157.5%
78.75%
15.75%
@ 5.5V
/ R
W
The slope of the resistance has a linear area (at the
higher voltages) and a non-linear area (at the lower
voltages), where resistance increases faster than the
voltage drop (at low voltages).
FIGURE 6-4:
Resistance (R
Since there is minimal variation of the total device
resistance over voltage, at a constant temperature (see
Figure
the change in wiper resistance over voltage can have a
significant impact on the INL and DNL error.
= Max
S
(%)
Note:
R
W
(1)
2-6,
R
204.75%
975.0%
409.5%
40.95%
@ 2.7V
W
= Max
Figure
The slope of the resistance has a linear
area (at the higher voltages) and a non-
linear area (at the lower voltages).
W
) to Voltage
2-17,
Typical
3.57%
0.75%
0.15%
Relationship of Wiper
R
1.5%
© 2006 Microchip Technology Inc.
W
Figure 2-27
=
R
W
V
R
DD
/ R
@ 5.5V
W
5.95%
2.50%
1.25%
0.25%
AB
= Max
or
(%)
Figure
(2)
R
15.48%
@ 2.7V
W
6.50%
3.25%
0.65%
= Max
2-37),