PIC12F752 datasheet(109/204 Pages) MICROCHIP

109 / 204 page

 2011 Microchip Technology Inc.

Preliminary

DS41576A-page 109

PIC12F752/HV752

13.0

FIXED VOLTAGE REFERENCE

(FVR)

The Fixed Voltage Reference (FVR) is a stable voltage

reference, independent of VDD, 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

FVRBUFSS

DACOE

FVRBUFEN

FVREN

12HV752

1.2V

ref

rdy

FVRRDY

fvr_ref

VSS

VDD

dac_ref

DACEN

DACR<4:0>

DACPSS

DAC

DACRNG

Vss

PIC12HV752 only

5V Shunt

Regulator

To ADC, Comparators

C1 and C2.

To ADC, Comparators

C1 and C2.

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