PIC16F676 Microchip Technology Inc., PIC16F676 Datasheet - Page 42

• Manufacturer Part Number: PIC16F676
• Description: 14-pin, Flash-based 8-bit Cmos Microcontroller
• Manufacturer: Microchip Technology Inc.

PIC16F630/676
6.3
A simplified circuit for an analog input is shown in
Figure 6-3. Since the analog pins are connected to a
digital output, they have reverse biased diodes to V
and V
V
FIGURE 6-3:
6.4
The comparator output, COUT, is read through the
CMCON register. This bit is read-only. The comparator
output may also be directly output to the RA2 pin in
three of the eight possible modes, as shown in
Figure 6-2. When in one of these modes, the output on
RA2 is asynchronous to the internal clock. Figure 6-4
shows the comparator output block diagram.
FIGURE 6-4:
DS40039E-page 40
SS
and V
SS
. The analog input, therefore, must be between
Analog Input Connection
Considerations
Comparator Output
To RA2/T0CKI pin
DD
. If the input voltage deviates from this
VA
Legend:
To Data Bus
Rs < 10K
Set CMIF bit
ANALOG INPUT MODE
MODIFIED COMPARATOR OUTPUT BLOCK DIAGRAM
RD CMCON
A
IN
C
V
I
R
R
VA
LEAKAGE
T
PIN
IC
S
C
5 pF
PIN
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to Various Junctions
= Interconnect Resistance
= Source Impedance
= Analog Voltage
Q
Q
DD
V
DD
EN
EN
V
V
T
D
D
T
= 0.6V
= 0.6V
RESET
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latchup may occur. A
maximum
recommended for the analog sources. Any external
component connected to an analog input pin, such as
a capacitor or a Zener diode, should have very little
leakage current.
The TRISA<2> bit functions as an output enable/
disable for the RA2 pin while the comparator is in an
Output mode.
RD CMCON
Note 1: When reading the PORTA register, all
2: Analog levels on any pin that is defined as
Leakage
±500 nA
Vss
pins configured as analog inputs will read
as a ‘0’. Pins configured as digital inputs
will convert an analog input according to
the TTL input specification.
a digital input, may cause the input buffer
to consume more current than is
specified.
source
CINV
R
IC
impedance
© 2007 Microchip Technology Inc.
CM2:CM0
RA0/CIN+
RA1/CIN-
CV
of
REF
10 kΩ
is