PIC18F2455T-I/ML View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC18F2455T-I/ML

28/40/44-Pin, High-Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

Microchip Technology 

PIC18F2455/2550/4455/4550

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 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 22-4:

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 22-1: 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

55

CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0

55

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF

53

PIR2

OSCFIF

CMIF

USBIF

EEIF

BCLIF HLVDIF TMR3IF CCP2IF

56

PIE2

OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56

IPR2

PORTA

LATA

TRISA

OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56

—

RA6(1)

RA5

RA4

RA3

RA2

RA1

RA0

56

—

LATA6(1) LATA5 LATA4 LATA3 LATA2 LATA1 LATA0

56

—

TRISA6(1) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0

56

Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.

Note 1: PORTA<6> and its direction and latch bits are individually configured as port pins based on various

oscillator modes. When disabled, these bits read as ‘0’.

© 2009 Microchip Technology Inc.

DS39632E-page 279

Share Link: