Datasheet

 2011-2013 Microchip Technology Inc. DS40001609B-page 129
PIC16(L)F1508/9
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.
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 30-65.
FIGURE 13-1: VOLTAGE REFERENCE BLOCK DIAGRAM
ADFVR<1:0>
CDAFVR<1:0>
X1
X2
X4
X1
X2
X4
2
2
FVR_buffer1
(To ADC Module)
FVR_buffer2
(To Comparators)
+
_
FVREN
FVRRDY
Any peripheral requiring the
Fixed Reference
(See Table 13-1)
VADFVR
VCDAFVR
VFVR
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.