PIC17C7XX_13 Datasheet, PDF (185/306 Pages) Microchip Technology – High-Performance 8-bit CMOS EPROM Microcontrollers with 10-bit A/D

PIC17C7XX
16.2 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:
• 8TOSC
• 32TOSC
• 64TOSC
• Internal 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 s.
Table 16-1 and Table 16-2 show the resultant TAD times
derived from the device operating frequencies and the
A/D clock source selected. These times are for stan-
dard voltage range devices.
TABLE 16-1: TAD vs. DEVICE OPERATING FREQUENCIES (STANDARD DEVICES (C))
Note:
AD Clock Source (TAD)
Operation
ADCS1:ADCS0
Max FOSC
(MHz)
8TOSC
00
5
32TOSC
01
20
64TOSC
10
33
RC
11
—
When the device frequency is greater than 1 MHz, the RC A/D conversion clock source is only
recommended for SLEEP operation.
TABLE 16-2: TAD vs. DEVICE OPERATING FREQUENCIES (EXTENDED VOLTAGE DEVICES (LC))
Note:
AD Clock Source (TAD)
Operation
ADCS1:ADCS0
Max FOSC
(MHz)
8TOSC
00
2.67
32TOSC
01
10.67
64TOSC
10
21.33
RC
11
—
When the device frequency is greater than 1 MHz, the RC A/D conversion clock source is only
recommended for SLEEP operation.
 1998-2013 Microchip Technology Inc.
DS30289C-page 185