Datasheet

Table Of Contents
© 2008 Microchip Technology Inc. DS41262E-page 117
PIC16F631/677/685/687/689/690
FIGURE 9-4: ANALOG INPUT MODEL
FIGURE 9-5: ADC TRANSFER FUNCTION
Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself out.
2: The charge holding capacitor (C
HOLD) is not discharged after each conversion.
3: The maximum recommended impedance for analog sources is 10 kΩ. This is required to meet the pin
leakage specification.
CPIN
VA
Rs
ANx
5 pF
V
DD
VT = 0.6V
V
T = 0.6V
I LEAKAGE
(1)
RIC 1k
Sampling
Switch
SS
Rss
C
HOLD = 10 pF
V
SS/VREF-
6V
Sampling Switch
5V
4V
3V
2V
567891011
(kΩ)
V
DD
Legend: CPIN
VT
I LEAKAGE
RIC
SS
C
HOLD
= Input Capacitance
= Threshold Voltage
= Leakage current at the pin due to
= Interconnect Resistance
= Sampling Switch
= Sample/Hold Capacitance
various junctions
RSS
Note 1: See Section 17.0 “Electrical Specifications”.
3FFh
3FEh
ADC Output Code
3FDh
3FCh
004h
003h
002h
001h
000h
Full-Scale
3FBh
1 LSB ideal
VSS/VREF-
Zero-Scale
Transition
V
DD/VREF+
Transition
1 LSB ideal
Full-Scale Range
Analog Input Voltage