PIC16F1507-ESLASHSS. datasheet(118/278 Pages) MICROCHIP

118 / 278 page

PIC16(L)F1507

DS40001586D-page 118

 2011-2015 Microchip Technology Inc.

15.1

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

15.1.1

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 to Section

11.0 “I/O Ports”

for more information.

15.1.2

CHANNEL SELECTION

There are 14 channel selections available:

•AN<11:0> pins

• Temperature Indicator

• FVR_buffer1

The CHS bits of the ADCON0 register determine which

channel is connected to the sample and hold circuit.

When changing channels, a delay (TACQ) is required

before starting the next conversion. Refer to Section

15.2.6 “ADC Conversion Procedure”

for more infor-

mation.

15.1.3

ADC VOLTAGE REFERENCE

The ADC module uses a positive and a negative

voltage reference. The positive reference is labeled

ref+ and the negative reference is labeled ref-.

The positive voltage reference (ref+) is selected by the

ADPREF bits in the ADCON1 register. The positive

voltage reference source can be:

•VREF+ pin

•VDD

The negative voltage reference (ref-) source is:

•VSS

15.1.4

CONVERSION CLOCK

The source of the conversion clock is software select-

able 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 (internal RC 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 15-2.

For correct conversion, the appropriate TAD specifica-

tion must be met. Refer to the ADC conversion require-

ments in Section 25.0 “Electrical Specifications” for

more information. Table 15-1 gives examples of

appropriate ADC clock selections.

Note:

Analog voltages on any pin that is defined

as a digital input may cause the input

buffer 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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