PIC18F87J90 Datasheet, PDF (303/450 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F87J90 FAMILY
22.9 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 22-4. 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 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 22-4:
COMPARATOR ANALOG INPUT MODEL
VDD
RS < 10k
AIN
VA
CPIN
5 pF
VT = 0.6V
VT = 0.6V
RIC
ILEAKAGE
±100 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 22-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF
PIR2
OSCFIF CMIF
—
—
BCLIF LVDIF TMR3IF
—
PIE2
OSCFIE CMIE
—
—
BCLIE LVDIE TMR3IE
—
IPR2
OSCFIP CMIP
—
—
BCLIP LVDIP TMR3IP
—
CMCON
C2OUT C1OUT C2INV C1INV
CIS
CM2
CM1
CM0
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0
PORTF
RF7
RF6
RF5
RF4
RF3
RF2
RF1
—
LATF
LATF7
LATF6 LATF5 LATF4 LATF3 LATF2 LATF1
—
TRISF
TRISF7 TRISF6 TRISF5 TRISF4 TRISF3 TRISF2 TRISF1
—
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.
Reset
Values
on page
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 2010 Microchip Technology Inc.
DS39933D-page 303