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| PIC18F2480_09 Datasheet, PDF (267/490 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with ECAN Technology, 10-Bit A/D and nanoWatt Technology | |||
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PIC18F2480/2580/4480/4580
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
VT = 0.6V
RIC
AIN
VA
CPIN
5 pF
VT = 0.6V
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 21-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
CMCON(3) C2OUT
CVRCON(3) CVREN
C1OUT
CVROE
C2INV C1INV
CVRR CVRSS
CIS
CVR3
CM2
CVR2
CM1
CVR1
CM0
CVR0
INTCON
IPR2
PIR2
PIE2
PORTA
LATA
TRISA
GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE
OSCFIP CMIP(2)
â
EEIP BCLIP
OSCFIF CMIF(2)
â
EEIF BCLIF
OSCFIE CMIE(2)
â
EEIE BCLIE
RA7(1)
RA6(1)
RA5
RA4
RA3
LATA7(1) LATA6(1) LATA Data Output Register
TRISA7(1) TRISA6(1) PORTA Data Direction Register
TMR0IF
HLVDIP
HLVDIF
HLVDIE
RA2
INT0IF
TMR3IP
TMR3IF
TMR3IE
RA1
RBIF
ECCP1IP
ECCP1IF
ECCP1IE
RA0
Legend: â = unimplemented, read as â0â. Shaded cells are unused by the comparator module.
Note 1: PORTA pins are enabled based on oscillator configuration.
2: These bits are available in PIC18F4X80 devices and reserved in PIC18F2X80 devices.
3: These registers are unimplemented on PIC18F2X80 devices.
Reset
Values
on Page:
57
57
58
57
58
58
58
58
58
© 2009 Microchip Technology Inc.
DS39637D-page 267
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