Datasheet

© 2009 Microchip Technology Inc. DS39682E-page 229
PIC18F45J10 FAMILY
19.9 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 19-4. 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
V
SS 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 19-4: COMPARATOR ANALOG INPUT MODEL
TABLE 19-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 49
CVRCON CVREN CVROE CVRR
CVRSS CVR3 CVR2 CVR1 CVR0 49
INTCON GIE/GIEH PEIE/GIEL
TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 50
PIR2
OSCFIF CMIF — — BCL1IF — — CCP2IF 49
PIE2 OSCFIE CMIE — — BCL1IE — — CCP2IE 49
IPR2
OSCFIP CMIP — — BCL1IP — — CCP2IP 49
PORTA — —RA5— RA3 RA2 RA1 RA0 50
LATA — — PORTA Data Latch Register (Read and Write to Data Latch) 50
TRISA
— — TRISA5 — TRISA3 TRISA2 TRISA1 TRISA0 50
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.
VA
R
S < 10k
A
IN
CPIN
5 pF
V
DD
VT = 0.6V
VT = 0.6V
RIC
ILEAKAGE
±100 nA
V
SS
Legend: CPIN = Input Capacitance
V
T = Threshold Voltage
I
LEAKAGE = Leakage Current at the pin due to various junctions
R
IC = Interconnect Resistance
R
S = Source Impedance
VA = Analog Voltage
Comparator
Input