Datasheet

 2008-2013 Microchip Technology Inc. DS22096B-page 93
MCP453X/455X/463X/465X
APPENDIX B: CHARACTERIZATION
DATA ANALYSIS
Some designers may desire to understand the device
operational characteristics outside of the specified
operating conditions of the device.
Applications where the knowledge of the resistor
network characteristics could be useful include battery
powered devices and applications that experience
brown-out conditions.
In battery applications, the application voltage decays
over time until new batteries are installed. As the
voltage decays, the system will continue to operate. At
some voltage level, the application will be below its
specified operating voltage range. This is dependent
on the individual components used in the design. It is
still useful to understand the device characteristics to
expect when this low-voltage range is encountered.
Unlike a microcontroller, which can use an external
supervisor device to force the controller into the Reset
state, a digital potentiometer’s resistance characteristic
is not specified. But understanding the operational
characteristics can be important in the design of the
application’s circuit for this low-voltage condition.
Other application system scenarios, where under-
standing the low-voltage characteristics of the resistor
network could be important, is for system brown-out
conditions.
For the MCP453X/455X/463X/465X devices, the ana-
log operation is specified at a minimum of 2.7V. Device
testing has Terminal A connected to the device V
DD
(for
potentiometer configuration only) and Terminal B
connected to V
SS
.
B.1 Low-Voltage Operation
This appendix gives an overview of CMOS
semiconductor characteristics at lower voltages. This is
important so that the 1.8V resistor network
characterization graphs of the MCP453X/455X/463X/
465X devices can be better understood.
For this discussion, we will use the 5 k device data.
This data was chosen since the variations of wiper
resistance has much greater implications for devices
with smaller R
AB
resistances.
Figure B-1 shows the worst case R
BW
error from the
average R
BW
as a percentage, while Figure B-2 shows
the R
BW
resistance versus wiper code graph. Nonlinear
behavior occurs at approximately wiper code 160. This
is better shown in Figure B-2, where the R
BW
resistance changes from a linear slope. This change is
due to the change in the wiper resistance.
FIGURE B-1: 1.8V Worst Case R
BW
Error
from Average R
BW
(R
BW0
-R
BW3
) vs. Wiper Code
and Temperature (V
DD
= 1.8V, I
W
= 190 µA).
FIGURE B-2: R
BW
vs. Wiper Code And
Temperature (V
DD
= 1.8V, I
W
= 190 µA).
-7.00%
-6.00%
-5.00%
-4.00%
-3.00%
-2.00%
-1.00%
0.00%
1.00%
2.00%
0 32 64 96 128 160 192 224 256
Wiper Code
Error %
-40C
+25C
+85C
+125C
0
1000
2000
3000
4000
5000
6000
7000
0 32 64 96 128 160 192 224 256
Wiper Code
Resistance ()
-40C
+25C
+85C
+125C