PIC16F526 Datasheet, PDF (66/122 Pages) Microchip Technology – 14-Pin, 8-Bit Flash Microcontroller

PIC16F526
10.1 Comparator Operation
A single comparator is shown in Figure 10-2 along with
the relationship between the analog input levels and
the digital output. When the analog input at VIN+ is less
than the analog input VIN-, the output of the comparator
is a digital low level. The shaded area of the output of
the comparator in Figure 10-2 represent the
uncertainty due to input offsets and response time. See
Table 14-2 for Common Mode Voltage.
FIGURE 10-2:
SINGLE COMPARATOR
VIN+
+
VIN-
–
Result
VIN-
VIN+
Result
10.2 Comparator Reference
An internal reference signal may be used depending on
the comparator operating mode. The analog signal that
is present at VIN- is compared to the signal at VIN+, and
the digital output of the comparator is adjusted
accordingly (Figure 10-2). Please see Section 11.0
“Comparator Voltage Reference Module” for internal
reference specifications.
10.3 Comparator Response Time
Response time is the minimum time after selecting a
new reference voltage or input source before the
comparator output is to have a valid level. If the
comparator inputs are changed, a delay must be used
to allow the comparator to settle to its new state.
Please see Table 14-3 for comparator response time
specifications.
10.4 Comparator Output
The comparator output is read through the CM1CON0
or CM2CON0 register. This bit is read-only. The
comparator output may also be used externally, see
Figure 10-1.
Note:
Analog levels on any pin that is defined as
a digital input may cause the input buffer
to consume more current than is specified.
10.5 Comparator Wake-up Flag
The Comparator Wake-up Flag is set whenever all of
the following conditions are met:
• C1WU = 0 (CM1CON0<0>) or
C2WU = 0 (CM2CON0<0>)
• CM1CON0 or CM2CON0 has been read to latch
the last known state of the C1OUT and C2OUT bit
(MOVF CM1CON0, W)
• Device is in Sleep
• The output of a comparator has changed state
The wake-up flag may be cleared in software or by
another device Reset.
10.6 Comparator Operation During
Sleep
When the comparator is enabled it is active. To
minimize power consumption while in Sleep mode, turn
off the comparator before entering Sleep.
10.7 Effects of Reset
A Power-on Reset (POR) forces the CM2CON0
register to its Reset state. This forces the Comparator
input pins to analog Reset mode. Device current is
minimized when analog inputs are present at Reset
time.
10.8 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 10-3. 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
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. Any external
component connected to an analog input pin, such as
a capacitor or a Zener diode, should have very little
leakage current.
DS41326D-page 66
 2010 Microchip Technology Inc.