Microchip Technology MCP1631RD-MCC2 Data Sheet
2006-2012 Microchip Technology Inc.
DS41291G-page 95
PIC16F882/883/884/886/887
8.7
Analog Input Connection
Considerations
Considerations
A simplified circuit for an analog input is shown in
. Since the analog input pins share their
connection with a digital input, they have reverse
biased ESD protection diodes to V
biased ESD protection diodes to V
DD
and V
SS
. The
analog input, therefore, must be between V
SS
and V
DD
.
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
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.
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 8-6:
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.
‘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.
consume more current than is specified.
V
A
Rs < 10K
C
PIN
5 pF
V
DD
V
T
0.6V
V
T
0.6V
R
IC
I
LEAKAGE(1)
±500 nA
Vss
A
IN
Legend: C
PIN
= 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 ADC Input
Note 1: See