Datasheet

 2011-2013 Microchip Technology Inc. DS40001441D-page 145
PIC12(L)F1840
19.7 Comparator Negative Input
Selection
The C1NCH bit of the CM1CON1 register directs one
of two analog pins to the comparator inverting input.
19.8 Comparator Response Time
The comparator output is indeterminate for a period of
time after the change of an input source or the selection
of a new reference voltage. This period is referred to as
the response time. The response time of the comparator
differs from the settling time of the voltage reference.
Therefore, both of these times must be considered when
determining the total response time to a comparator
input change. See the Comparator and Voltage
Reference Specifications in
Section 30.0 “Electrical
Specifications”
for more details.
19.9 Interaction with ECCP Logic
The C1 comparator can be used as a general purpose
comparator. The output can be brought out to the
C1OUT pin. When the ECCP auto-shutdown is active
it can use the comparator signal. If auto-restart is also
enabled, the comparator can be configured as a
closed loop analog feedback to the ECCP, thereby,
creating an analog controlled PWM.
19.10 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 19-3. 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.
Note: To use C1IN+ and C1INx- pins as analog
input, the appropriate bits must be set in
the ANSEL register and the correspond-
ing TRIS bits must also be set to disable
the output drivers.
Note: When the comparator module is first
initialized the output state is unknown.
Upon initialization, the user should verify
the output state of the comparator prior to
relying on the result, primarily when using
the result in connection with other
peripheral features, such as the ECCP
Auto-Shutdown mode.
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.