PIC18F258 MICROCHIP [Microchip Technology], PIC18F258 Datasheet - Page 251

• Manufacturer Part Number: PIC18F258
• Description: High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN
• Manufacturer: MICROCHIP [Microchip Technology]

21.7
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.
FIGURE 21-4:
2002 Microchip Technology Inc.
Comparator Operation During
SLEEP
VA
Legend:
R
S
< 10k
ANALOG INPUT MODEL
A
IN
C
V
I
R
R
VA
LEAKAGE
T
PIN
IC
S
C
5 pF
PIN
=
=
=
=
=
=
Input Capacitance
Threshold Voltage
Leakage Current at the pin due to various junctions
Interconnect Resistance
Source Impedance
Analog Voltage
Preliminary
V
DD
V
V
T
T
= 0.6V
= 0.6V
21.8
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
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 V
and V
V
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latchup condition may
occur. A maximum source impedance of 10 k
ommended for the analog sources. Any external com-
ponent connected to an analog input pin, such as a
capacitor or a Zener diode, should have very little
leakage current.
SS
and V
SS
. The analog input, therefore, must be between
Effects of a RESET
Analog Input Connection
Considerations
I
V
LEAKAGE
500 nA
DD
SS
. If the input voltage deviates from this
R
IC
PIC18FXX8
DS41159B-page 249
is rec-
DD