PIC18F1XK22 Datasheet, PDF (229/388 Pages) Microchip Technology – 20-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC18F1XK22/LF1XK22
17.7 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 17-6. Since the analog input pins share their
connection with a digital input, they have reverse
biased ESD protection 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 may occur.
A maximum source impedance of 10 k is recommended
for the analog sources. Also, any external component
connected to an analog input pin, such as a capacitor or
a Zener diode, should have very little leakage current to
minimize inaccuracies introduced.
FIGURE 17-6:
ANALOG INPUT MODEL
VDD
Rs < 10K
VA
AIN
CPIN
5 pF
VT  0.6V
VT  0.6V
Note 1: When reading a PORT register, all pins
configured as analog inputs will read as a
‘0’. Pins configured as digital inputs will
convert as an analog input, according to
the input specification.
2: Analog levels on any pin defined as a
digital input, may cause the input buffer to
consume more current than is specified.
RIC
ILEAKAGE⁽¹⁾
Vss
Legend:
CPIN = Input Capacitance
ILEAKAGE = Leakage Current at the pin due to various junctions
RIC
= Interconnect Resistance
RS
= Source Impedance
VA
= Analog Voltage
VT
= Threshold Voltage
Note 1: See Section 25.0 “Electrical Specifications”.
 2010 Microchip Technology Inc.
Preliminary
DS41365D-page 229