PIC12F629/675
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latch-up may occur. A
6.3
Analog Input Connection
Considerations
maximum
source
impedance
of
10 k
is
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 VDD
and VSS. The analog input, therefore, must be between
VSS and VDD. If the input voltage deviates from this
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.
FIGURE 6-3:
ANALOG INPUT MODE
VDD
VT = 0.6V
RIC
Rs < 10K
AIN
Leakage
±500 nA
CPIN
5 pF
VA
VT = 0.6V
Vss
Legend:
CPIN
VT
= Input Capacitance
= Threshold Voltage
ILEAKAGE
RIC
= Leakage Current at the pin due to Various Junctions
= Interconnect Resistance
RS
= Source Impedance
VA
= Analog Voltage
The TRISIO<2> bit functions as an output enable/
disable for the GP2 pin while the comparator is in an
Output mode.
6.4
Comparator Output
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 GP2 pin in
three of the eight possible modes, as shown in
Figure 6-2. When in one of these modes, the output on
GP2 is asynchronous to the internal clock. Figure 6-4
shows the comparator output block diagram.
Note 1: When reading the GPIO register, all 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.
2: Analog levels on any pin that is defined as
a digital input, may cause the input buffer
to consume more current than is
specified.
FIGURE 6-4:
MODIFIED COMPARATOR OUTPUT BLOCK DIAGRAM
GP0/CIN+
GP1/CIN-
CVREF
To GP2/T0CKI pin
To Data Bus
RD CMCON
Q
Q
D
EN
CINV
CM2:CM0
Set CMIF bit
D
RD CMCON
EN
Reset
DS41190G-page 40
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
