Datasheet

 2011 Microchip Technology Inc. Preliminary DS41441B-page 123
PIC12(L)F1840
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
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 module 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 16.0 “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 Comparators, DAC,
and CPS module. Reference Section 17.0 “Digital-to-
Analog Converter (DAC) Module”, Section 19.0
“Comparator Module” and Section 17.0 “Digital-to-
Analog Converter (DAC) 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 30.0 “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, CPS)
+
_
FVREN
FVRRDY
1.024V Fixed
Reference