Datasheet

 2010-2012 Microchip Technology Inc. DS41452C-page 131
PIC16(L)F1516/7/8/9
14.0 FIXED VOLTAGE REFERENCE
(FVR)
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
The FVR can be enabled by setting the FVREN bit of
the FVRCON register.
14.1 Independent Gain Amplifiers
The output of the FVR supplied to the ADC module is
routed through a programmable gain amplifier. The
amplifier can be configured to amplify the reference
voltage by 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”
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 25.0 “Electrical Specifications” for the
minimum delay requirement.
FIGURE 14-1: VOLTAGE REFERENCE BLOCK DIAGRAM
FVR BUFFER1
(To ADC Module)
x1
x2
x4
+
-
1.024V Fixed
Reference
FVREN
FVRRDY
2
ADFVR<1:0>
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> = 100 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 PIC16F1516/7/8/9 devices, when
VREGPM = 1 and not in Sleep
The device runs off of the low-power regulator when in Sleep
mode.