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
00
1.25 MHz
8TOSC
01
5 MHz
32TOSC
RC(1, 2, 3)
10
20 MHz
11
(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.
2001 Microchip Technology Inc.
Preliminary
DS39544A-page 79