41594B datasheet(121/372 Pages) MICROCHIP

121 / 372 page

 2011-2012 Microchip Technology Inc.

Preliminary

DS41594B-page 121

PIC12LF1840T48A

14.0 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)

• 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 31.0 “Electrical Specifications” for the

minimum delay requirement.

FIGURE 14-1:

VOLTAGE REFERENCE BLOCK DIAGRAM

ADFVR<1:0>

CDAFVR<1:0>

FVR BUFFER1

(To ADC Module)

FVR BUFFER2

(To Comparators, DAC, CPS)

FVREN

FVRRDY

1.024V Fixed

Reference

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