PIC18F23K22 Datasheet, PDF (337/492 Pages) Microchip Technology – 28/40/44-Pin, Low-Power, High-Performance Microcontrollers with nanoWatt XLP Technology

PIC18(L)F2X/4XK22
21.0 FIXED VOLTAGE REFERENCE
(FVR)
The Fixed Voltage Reference, or FVR, is a stable
voltage reference, independent of VDD, 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)
The FVR can be enabled by setting the FVREN bit of
the VREFCON0 register.
21.1 Independent Gain Amplifiers
The output of the FVR supplied to the ADC,
Comparators and DAC is routed through an
independent programmable gain amplifier. The
amplifier can be configured to amplify the 1.024V
reference voltage by 1x, 2x or 4x, to produce the three
possible voltage levels.
The FVRS<1:0> bits of the VREFCON0 register are
used to enable and configure the gain amplifier settings
for the reference supplied to the DAC and Comparator
modules. When the ADC module is configured to use
the FVR output, (FVR BUF2) the reference is buffered
through an additional unity gain amplifier. This buffer is
disabled if the ADC is not configured to use the FVR.
For specific use of the FVR, refer to the specific module
sections: Section 17.0 “Analog-to-Digital Converter
(ADC) Module”, Section 22.0 “Digital-to-Analog
Converter (DAC) Module” and Section 18.0 “Com-
parator Module”.
21.2 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 FVRST bit of the VREFCON0 register will be set. See
Section 27.0 “Electrical Characteristics” for the
minimum delay requirement.
FIGURE 21-1:
VOLTAGE REFERENCE BLOCK DIAGRAM
X1
FVRS<1:0> ₂
X1
X2
X4
FVREN
FVRST
+ _{1.024V Fixed}
_ _Reference
FVR BUF2
(To ADC Module)
FVR BUF1
(To Comparators, DAC)
 2010 Microchip Technology Inc.
Preliminary
DS41412B-page 337