Datasheet
2012 Microchip Technology Inc. Preliminary DS41639A-page 149
PIC16(L)F1454/5/9
14.0 FIXED VOLTAGE REFERENCE
(FVR) (PIC16(L)F1455/9 ONLY)
The Fixed Voltage Reference, or FVR, is a stable
voltage reference, independent of V
DD, with 1.024V,
2.048V or 4.096V selectable output levels. The output
of the FVR can be configured to supply a reference
voltage to the following:
• ADC input channel
• ADC positive reference
• DAC input channel
• Comparator positive input
• Comparator negative input
The FVR can be enabled by setting the FVREN bit of
the FVRCON register.
14.1 Independent Gain Amplifier
The output of the FVR supplied to the ADC and
comparators 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 16.0 “Analog-to-Digital Converter
(ADC) Module (PIC16(L)F1455/9 only)”
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 18.0 “Comparator Module
(PIC16(L)F1455/9 only)”
for additional information.
14.2 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
Section 29.0 “Electrical Specifications” for the
minimum delay requirement.
FIGURE 14-1: 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, DAC)
+
_
FVREN
FVRRDY
Any peripheral requiring the
Fixed Reference
(See Table 14-1)
TABLE 14-1: 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 PIC16F1454/5/9 devices, when
VREGPM = 1 and not in Sleep
The device runs off of the Low-Power Regulator when in
Sleep mode.