Datasheet
2011-2013 Microchip Technology Inc. DS40001574C-page 147
PIC16(L)F1938/9
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
• Comparator positive input
• Digital-to-Analog Converter (DAC)
• Capacitive Sensing (CPS) module
• LCD bias generator
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,
Comparators, DAC and CPS is routed through two
independent programmable gain amplifiers. Each
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 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 DAC, CPS and Comparator
module. Reference
Section 17.0 “Digital-to-Analog
Converter (DAC) Module”
, Section 18.0 “Comparator
Module”
and Section 26.0 “Capacitive Sensing (CPS)
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
in the applicable Electrical Specifications Chapter 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)
FVR VREF
(To LCD Bias Generator)
+
_
FVREN
FVRRDY
1.024V Fixed
Reference
Any peripheral requiring the
Fixed Reference
(See Table 14-1)