RFPIC12F675K Datasheet, PDF (38/136 Pages) Microchip Technology – 20-Pin FLASH-Based 8-Bit CMOS Microcontroller with UHF ASK/FSK Transmitter

rfPIC12F675
6.3 Analog Input Connection
Considerations
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
FIGURE 6-3:
ANALOG INPUT MODE
VDD
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latchup may occur. A
maximum source impedance of 10 kΩ is
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.
Rs < 10K
VT = 0.6V
RIC
AIN
VA
CPIN
5 pF
VT = 0.6V
Leakage
±500 nA
Legend:
CPIN
VT
ILEAKAGE
RIC
RS
VA
Vss
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to Various Junctions
= Interconnect Resistance
= Source Impedance
= Analog Voltage
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.
The TRISIO<2> bit functions as an output enable/
disable for the GP2 pin while the comparator is in an
Output mode.
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
To GP2/T0CKI pin
To Data Bus
RD CMCON
QD
EN
CINV
GP0/CIN+
GP1/CIN-
CVREF
CM2:CM0
Set CMIF bit
QD
EN
RD CMCON
RESET
DS70091A-page 36
Preliminary
 2003 Microchip Technology Inc.