PIC18FXX8 Datasheet, PDF (255/402 Pages) Microchip Technology – 28/40-Pin High-Performance, Enhanced Flash Microcontrollers with CAN Module

PIC18FXX8
21.7 Comparator Operation During
Sleep
When a comparator is active and the device is placed
in Sleep mode, the comparator remains active and the
interrupt is functional if enabled. This interrupt will
wake-up the device from Sleep mode when enabled.
While the comparator is powered up, higher Sleep
currents than shown in the power-down current
specification will occur. Each operational comparator
will consume additional current, as shown in the com-
parator specifications. To minimize power consumption
while in Sleep mode, turn off the comparators,
CM<2:0> = 111, before entering Sleep. If the device
wakes up from Sleep, the contents of the CMCON
register are not affected.
21.8 Effects of a Reset
A device Reset forces the CMCON register to its Reset
state, causing the comparator module to be in the
Comparator Reset mode, CM<2:0> = 000. This
ensures that all potential inputs are analog inputs.
Device current is minimized when analog inputs are
present at Reset time. The comparators will be
powered down during the Reset interval.
21.9 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 21-4. Since the analog pins are connected to a
digital output, they have reverse biased diodes to VDD
and VSS. The analog input, therefore, must be between
VSS and VDD. If the input voltage deviates from this
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latch-up condition may
occur. A maximum source impedance of 10 kΩ is
recommended for the analog sources. Any external
component connected to an analog input pin, such as
a capacitor or a Zener diode, should have very little
leakage current.
FIGURE 21-4:
ANALOG INPUT MODEL
VDD
RS < 10k
AIN
VA
CPIN
5 pF
VT = 0.6V
VT = 0.6V
RIC
I LEAKAGE
±500 nA
Legend:
VSS
CPIN
=
VT
=
I LEAKAGE =
RIC
=
RS
=
VA
=
Input Capacitance
Threshold Voltage
Leakage Current at the pin due to various junctions
Interconnect Resistance
Source Impedance
Analog Voltage
 2004 Microchip Technology Inc.
DS41159D-page 253