Datasheet
2011 Microchip Technology Inc. Preliminary DS41576B-page 113
PIC12F752/HV752
13.0 FIXED VOLTAGE REFERENCE
(FVR)
The Fixed Voltage Reference (FVR) is a stable voltage
reference, independent of V
DD, with 1.2V output level.
The output of the FVR can be configured to supply a
reference voltage to the following:
• ADC input channel
• Comparator 1 positive input (C1VP)
• Comparator 2 positive input (C2VP)
•REFOUT pin
On the PIC12F752, the FVR is enabled by setting the
FVREN bit of the FVRCON register. The FVR is always
enabled on the PIC12HV752 device.
13.1 Fixed Voltage Reference Output
The FVR output can be applied to the REFOUT pin by
setting the FVRBUFSS and FVRBUFEN bits of the
FVRCON register. The FVRBUFSS bit selects either
the FVR or DAC output reference to the REFOUT pin
buffer. The FVRBUFEN bit enables the output buffer to
the REFOUT pin.
Enabling the REFOUT pin automatically overrides any
digital input or output functions of the pin. Reading the
REFOUT pin when it has been configured for a refer-
ence voltage output will always return a ‘0’.
13.2 FVR Stabilization Period
When the Fixed Voltage Reference module is enabled, it
requires time for the reference circuit to stabilize. Once
the circuit stabilizes and is ready for use, the FVRRDY bit
of the FVRCON register will be set. See Section 20.0
“Electrical Specifications” for the minimum delay
requirement.
13.3 Operation During Sleep
When the device wakes up from Sleep through an inter-
rupt or a Watchdog Timer time-out, the contents of the
FVRCON register are not affected. To minimize current
consumption in Sleep mode, FVR the voltage reference
should be disabled.
13.4 Effects of a Reset
A device Reset clears the FVRCON register. As a result:
• The FVR module is disabled.
• The FVR voltage output is disabled on the
REFOUT pin.
FIGURE 13-1: VOLTAGE REFERENCE BLOCK DIAGRAM
VREF+
VDD
REFOUT
DACOUT
fvr_ref
dac_ref
0
1
FVRBUFSS
DACOE
FVRBUFEN
x1
FVREN
12HV752
+
1.2V
-
ref
rdy
FVRRDY
fvr_ref
V
SS
EN
VDD
dac_ref
DACEN
DACR<4:0>
DACPSS
DAC
EN
DACRNG
Vss
PIC12HV752 only
5V Shunt
Regulator
To ADC, Comparators
C1 and C2.
To ADC, Comparators
C1 and C2.