PIC18F87J10 Datasheet, PDF (263/394 Pages) Microchip Technology – 64/80-Pin High-Performance, 1-Mbit Flash Microcontrollers with nanoWatt Technology

PIC18F87J10 FAMILY
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:
COMPARATOR ANALOG INPUT MODEL
VDD
RS < 10k
AIN
VA
CPIN
5 pF
VT = 0.6V
VT = 0.6V
RIC
ILEAKAGE
±500 nA
Comparator
Input
VSS
Legend:
CPIN
=
VT
=
ILEAKAGE =
RIC
=
RS
=
VA
=
Input Capacitance
Threshold Voltage
Leakage Current at the pin due to various junctions
Interconnect Resistance
Source Impedance
Analog Voltage
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
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF
49
PIR2
OSCFIF CMIF
—
—
BCL1IF
—
TMR3IF CCP2IF
51
PIE2
OSCFIE CMIE
—
—
BCL1IE
—
TMR3IE CCP2IE 51
IPR2
OSCFIP CMIP
—
—
BCL1IP
—
TMR3IP CCP2IP 51
CMCON
C2OUT C1OUT C2INV C1INV
CIS
CM2
CM1
CM0
51
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0
51
PORTF
RF7
RF6
RF5
RF4
RF3
RF2
RF1
—
52
LATF
LATF7
LATF6 LATF5 LATF4 LATF3 LATF2 LATF1
—
52
TRISF
TRISF7 TRISF6 TRISF5 TRISF4 TRISF3 TRISF2 TRISF1
—
52
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.
 2005 Microchip Technology Inc.
Advance Information
DS39663A-page 261