Microchip Technology PIC12F1501, Manual

Page: 123 / 402

PIC16(L)F1508/9
DS40001609E-page 124

2011-2015 Microchip Technology Inc.
13.0 FIXED VOLTAGE REFERENCE
(FVR)
The Fixed Voltage Reference (FVR) is a stable voltage
reference, independent of V
DD
, with a nominal output
level ( V
FVR
) of 1.024V. The output of the FVR can be
configured to supply a reference voltage to the
following:
• ADC input channel
• Comparator positive input
• Comparator negative input
The FVR can be enabled by setting the FVREN bit of
the FVRCON register.
13.1 Independent Gain Amplifier
The output of the FVR supplied to the peripherals, (listed
above), is routed through a programmable gain amplifier.
Each amplifier can be programmed for a gain of 1x, 2x or
4x, to produce the three possible voltage levels.
The ADFVR<1:0> bits of the FVRCON register are
used to enable and configure the gain amplifier settings
for the reference supplied to the ADC module. Refer-
ence
Section 15.0 “Analog-to-Digital Converter
(ADC) Module”
for additional information.
The CDAFVR<1:0> bits of the FVRCON register are
used to enable and configure the gain amplifier settings
for the reference supplied to the comparator modules.
Reference
Section 17.0 “Comparator Module”
for
additional information.
To minimize current consumption when the FVR is
disabled, the FVR buffers should be turned off by
clearing the Buffer Gain Selection bits.
13.2 FVR Stabilization Period
When the Fixed Voltage Reference module is enabled,
it requires time for the reference and amplifier circuits
to stabilize. Once the circuits stabilize and are ready for
use, the FVRRDY bit of the FVRCON register will be
set. See the FVR Stabilization Period characterization
graph,
Figure 30-64 .
FIGURE 13-1: VOLTAGE REFERENCE BLOCK DIAGRAM
1x
2x
4x
1x
2x
4x
ADFVR<1:0>
CDAFVR<1:0>
FVR_buffer1
(To ADC Module)
FVR_buffer2
(To Comparators)
+
_
FVREN
FVRRDY
Note 1
2
2
Rev. 10-000053A
8/6/2013
TABLE 13-1: PERIPHERALS REQUIRING THE FIXED VOLTAGE REFERENCE (FVR)
Peripheral Conditions Description
HFINTOSC FOSC<2:0> =
010
and
IRCF<3:0> =
000x
INTOSC is active and device is not in Sleep.
BOR
BOREN<1:0> =
11
BOR always enabled.
BOREN<1:0> =
10
and BORFS =
1
BOR disabled in Sleep mode, BOR Fast Start enabled.
BOREN<1:0> =
01
and BORFS =
1
BOR under software control, BOR Fast Start enabled.
LDO All PIC16F1508/9 devices, when
VREGPM =
1
and not in Sleep
The device runs off of the Low-Power Regulator when in Sleep
mode.