PIC16C925SLASHCL datasheet(81/182 Pages) MICROCHIP

81 / 182 page

 2001 Microchip Technology Inc.

Preliminary

DS39544A-page 79

PIC16C925/926

10.2

Selecting the A/D Conversion

Clock

The A/D conversion time per bit is defined as TAD. The

A/D conversion requires a minimum 12TAD per 10-bit

conversion. The source of the A/D conversion clock is

software selected. The four possible options for TAD

are:

• 2TOSC

• 8TOSC

• 32TOSC

• Internal A/D module RC oscillator

For correct A/D conversions, the A/D conversion clock

(TAD) must be selected to ensure a minimum TAD time

of 1.6

µs.

Table 10-1 shows the resultant TAD times derived from

the device operating frequencies and the A/D clock

source selected.

TABLE 10-1:

TAD vs. MAXIMUM DEVICE OPERATING FREQUENCIES (STANDARD DEVICES (C))

AD Clock Source (TAD)

Maximum Device Frequency

Operation

ADCS<1:0>

Max.

2TOSC

1.25 MHz

8TOSC

5 MHz

32TOSC

20 MHz

RC(1, 2, 3)

(Note 1)

Note 1: The RC source has a typical TAD time of 4

µs, but can vary between 2-6 µs.

2: When the device frequencies are greater than 1 MHz, the RC A/D conversion clock source is only recom-

mended for SLEEP operation.

3: For extended voltage devices (LC), please refer to the Electrical Specifications section.

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