PIC16C781 datasheet(71/186 Pages) MICROCHIP

71 / 186 page

 2001 Microchip Technology Inc.

Preliminary

DS41171A-page 69

PIC16C781/782

9.0

ANALOG-TO-DIGITAL

CONVERTER (ADC) MODULE

The 8-bit ADC module, shown in Figure 9-1, has 10

inputs in the PIC16C781/782:

• 8 external channels, AN<7:0> (RA<3:0> and

RB<3:0>)

• 2 internal channels, VR and VDAC

The ADC allows conversion of an analog input signal to

a corresponding 8-bit digital value. The desired chan-

nel is connected to a Sample-and-Hold by the input

multiplexers. The output of the Sample-and-Hold cap-

tures a snapshot of the voltage and holds it for the

ADC. The ADC then generates the 8-bit result via suc-

cessive approximation.

The analog reference voltage (ADCREF) is software

selectable from the following options:

• The analog positive supply: AVDD

• The reference input for Comparator C1: VREF1

• The Voltage Reference module output: VR

• The DAC Converter module output: VDAC

The ADC has the unique feature of being able to oper-

ate while the device is in SLEEP mode. To operate in

SLEEP, the ADC conversion clock must be derived

from the ADC’s dedicated internal RC oscillator.

FIGURE 9-1:

ADC MODULE BLOCK DIAGRAM

RA0/AN0/OPA+

RA1/AN1/OPA-

RA2/AN2/VREF2

RB0/INT/AN4/VR

RB1/AN5/VDAC

RB2/AN6

RB3/AN7/OPA

RA3/AN3/VREF1

AVDD

VREF1

ADCREF

ADC

VDAC

VCFG<1:0>

ADON

GO/DONE

Sample

and

Hold

VOLTAGE COMPARATOR MODULE

OPA MODULE

DAC MODULE

VR MODULE

CHS<3:0>

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