PIC18F23K20-E/MLQTP MICROCHIP [Microchip Technology], PIC18F23K20-E/MLQTP Datasheet - Page 281

• Manufacturer Part Number: PIC18F23K20-E/MLQTP
• Description: 28/40/44-Pin Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

21.0
There are two independent voltage references
available:
• Programmable Comparator Voltage Reference
• 1.2V Fixed Voltage Reference
21.1
The Comparator Voltage Reference module provides
an internally generated voltage reference for the com-
parators. The following features are available:
• Independent from Comparator operation
• Two 16-level voltage ranges
• Output clamped to V
• Ratiometric with V
• 1.2 Fixed Reference Voltage (FVR)
The CVRCON register (Figure 21-1) controls the
Voltage Reference module shown in Figure 21-1.
21.1.1
The comparator voltage reference is independent of
the comparator configuration. Setting the CVREN bit of
the CVRCON register will enable the voltage reference
by allowing current to flow in the CV
When both the CVREN bit is cleared, current flow in the
CV
drain of the voltage reference peripheral.
21.1.2
The
voltage levels in each range. Range selection is
controlled by the CVRR bit of the CVRCON register.
The 16 levels are set with the CVR<3:0> bits of the
CVRCON register.
The CV
equations:
EQUATION 21-1:
The full range of V
the construction of the module. See Figure 21-1.
© 2007 Microchip Technology Inc.
CV
CV
CV
REF
CV
CV
CV
RR
RR
RSRC
voltage divider is disabled minimizing the power
REF
REF
REF
REF
=
=
VOLTAGE REFERENCES
Comparator Voltage Reference
=
0 (high range):
1 (low range):
INDEPENDENT OPERATION
OUTPUT VOLTAGE SELECTION
output voltage is determined by the following
=
=
voltage reference has 2 ranges with 16
V
DD
(VR<3:0>/24)
(CV
SS
RSRC
or [(V
DD
to V
CV
SS
/4) +
REF
DD
REF
+) - (V
cannot be realized due to
×
(VR<3:0> CV
OUTPUT VOLTAGE
CV
REF
RSRC
REF
-)]
voltage divider.
×
Advance Information
RSRC
/32)
21.1.3
The CV
power consumption by configuring CVRCON as
follows:
• CVREN = 0
• CVRR = 1
• CVR<3:0> = 0000
This allows the comparator to detect a zero-crossing
while not consuming additional CV
21.1.4
The comparator voltage reference is V
therefore, the CV
V
Voltage Reference can be found in Section 26.0
“Electrical Characteristics”.
21.1.5
The CV
device CV
CON register to ‘1’. Selecting the reference voltage for
output on the CV
digital output buffer and digital input threshold detector
functions of that pin. Reading the CV
has been configured for reference voltage output will
always return a ‘0’.
Due to the limited current drive capability, a buffer must
be used on the voltage reference output for external
connections to CV
buffering technique.
21.1.6
When the device wakes up from Sleep through an
interrupt or a Watchdog Timer time-out, the contents of
the CVRCON register are not affected. To minimize
current consumption in Sleep mode, the voltage
reference should be disabled.
21.1.7
A device Reset affects the following:
• Comparator voltage reference is disabled
• Fixed voltage reference is disabled
• CV
• The high-voltage range is selected
• The CVR<3:0> range select bits are cleared
PIC18F2XK20/4XK20
DD
. The tested absolute accuracy of the Comparator
REF
REF
REF
is removed from the CV
REF
OUTPUT CLAMPED TO V
OUTPUT RATIOMETRIC TO V
VOLTAGE REFERENCE OUTPUT
OPERATION DURING SLEEP
EFFECTS OF A RESET
output voltage can be set to Vss with no
voltage reference can be output to the
pin by setting the CVROE bit of the CVR-
REF
REF
REF
output changes with fluctuations in
. Figure 21-2 shows an example
pin automatically overrides the
REF
REF
DS41303B-page 279
pin
REF
module current.
DD
SS
derived and
pin when it
DD