Datasheet

 2010 Microchip Technology Inc. DS39635C-page 269
PIC18F6310/6410/8310/8410
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
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 k 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: COMPARATOR ANALOG INPUT MODEL
TABLE 21-1: 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 65
CVRCON CVREN CVROE CVRR
CVRSS CVR3 CVR2 CVR1 CVR0 65
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 63
PIR2
OSCFIF CMIF — — BCLIF HLVDIF TMR3IF CCP2IF 65
PIE2
OCSFIE CMIE — — BCLIE HLVDIE TMR3IE CCP2IE 65
IPR2 OSCFIP CMIP — — BCLIP HLVDIP TMR3IP CCP2IP 65
PORTF RF7 RF6 RF5 RF4 RF3 RF2 RF1 RF0 66
LATF LATF Output Latch Register 66
TRISF PORTF Data Direction Register 66
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
V
T = 0.6V
R
IC
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