PIC16LF1824 datasheet(138/440 Pages) MICROCHIP

138 / 440 page

PIC16(L)F1847

DS40001453D-page 138

Preliminary

 2011-2013 Microchip Technology Inc.

16.1

ADC Configuration

When configuring and using the ADC the following

functions must be considered:

• Port configuration

• Channel selection

• ADC voltage reference selection

• ADC conversion clock source

• Interrupt control

• Result formatting

16.1.1

PORT CONFIGURATION

The ADC can be used to convert both analog and

digital signals. When converting analog signals, the I/O

pin should be configured for analog by setting the

associated

TRIS

and

ANSEL

bits.

Refer

Section 12.0 “I/O Ports” for more information.

16.1.2

CHANNEL SELECTION

There are up to 14 channel selections available:

•AN<11:0> pins

• DAC Output

• FVR (Fixed Voltage Reference) Output

Refer to Section 17.0 “Digital-to-Analog Converter

(DAC) Module” and Section 14.0 “Fixed Voltage

Reference (FVR)” for more information on these

channel selections.

The CHS bits of the ADCON0 register determine which

channel is connected to the sample and hold circuit.

When changing channels, a delay is required before

starting the next conversion. Refer to Section 16.2

“ADC Operation” for more information.

16.1.3

ADC VOLTAGE REFERENCE

The ADPREF bits of the ADCON1 register provides

control of the positive voltage reference. The positive

voltage reference can be:

•VREF+ pin

•VDD

• FVR 2.048V

• FVR 4.096V (Not available on LF devices)

The ADNREF bits of the ADCON1 register provides

control of the negative voltage reference. The negative

voltage reference can be:

•VREF- pin

•VSS

See Section 14.0 “Fixed Voltage Reference (FVR)”

for more details on the Fixed Voltage Reference.

16.1.4

CONVERSION CLOCK

The source of the conversion clock is software

selectable via the ADCS bits of the ADCON1 register.

There are seven possible clock options:

•FOSC/2

•FOSC/4

•FOSC/8

•FOSC/16

•FOSC/32

•FOSC/64

•FRC (dedicated internal oscillator)

The time to complete one bit conversion is defined as

TAD. One full 10-bit conversion requires 11.5 TAD

periods as shown in Figure 16-2.

For

correct

conversion,

the

appropriate

TAD

specification must be met. Refer to the ADC conversion

requirements

Section 30.0

“Electrical

Specifications” for more information. Table 16-1 gives

examples of appropriate ADC clock selections.

Note:

Analog voltages on any pin that is defined

as a digital input may cause the input buf-

fer to conduct excess current.

Note:

Unless using the FRC, any changes in the

system clock frequency will change the

ADC

clock

frequency,

which

may

adversely affect the ADC result.

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