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| PIC16F631_08 Datasheet, PDF (119/306 Pages) Microchip Technology – 20-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology | |||
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PIC16F631/677/685/687/689/690
Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself out.
2: The charge holding capacitor (CHOLD) 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.
FIGURE 9-4:
ANALOG INPUT MODEL
Rs ANx
VDD
VT = 0.6V
RIC ⤠1k
Sampling
Switch
SS Rss
VA
CPIN
5 pF
VT = 0.6V
I LEAKAGE(1)
CHOLD = 10 pF
VSS/VREF-
Legend: CPIN
= Input Capacitance
VT
= Threshold Voltage
I LEAKAGE = Leakage current at the pin due to
various junctions
RIC
= Interconnect Resistance
SS
= Sampling Switch
CHOLD = Sample/Hold Capacitance
Note 1: See Section 17.0 âElectrical Specificationsâ.
6V
5V
RSS
VDD 4V
3V
2V
5 6 7 8 9 10 11
Sampling Switch
(kΩ)
FIGURE 9-5:
ADC TRANSFER FUNCTION
3FFh
3FEh
3FDh
3FCh
3FBh
004h
003h
002h
001h
000h
VSS/VREF-
Full-Scale Range
1 LSB ideal
Zero-Scale
Transition
1 LSB ideal
Full-Scale
Transition
Analog Input Voltage
VDD/VREF+
© 2008 Microchip Technology Inc.
DS41262E-page 117
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