Datasheet

PIC16(L)F1782/3
DS41579D-page 178 Preliminary  2011-2012 Microchip Technology Inc.
20.10 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 20-4. Since the analog input pins share their
connection with a digital input, they have reverse
biased ESD protection diodes to V
DD and VSS. The
analog input, therefore, must be between V
SS 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.
20.10.1 ALTERNATE PIN LOCATIONS
This module incorporates I/O pins that can be moved to
other locations with the use of the alternate pin function
register APFCON. To determine which pins can be
moved and what their default locations are upon a
Reset, see
Section 13.1 “Alternate Pin Function” for
more information.
FIGURE 20-4: ANALOG INPUT MODEL
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.
VA
Rs < 10K
C
PIN
5 pF
V
DD
VT  0.6V
V
T  0.6V
R
IC
ILEAKAGE
(1)
Vss
Legend: CPIN = Input Capacitance
I
LEAKAGE = Leakage Current at the pin due to various junctions
R
IC = Interconnect Resistance
R
S = Source Impedance
V
A = Analog Voltage
V
T = Threshold Voltage
To Comparator
Note 1: See Section 30.0 “Electrical Specifications”
Analog
Input
pin