Datasheet

PIC18F2585/2680/4585/4680
DS39625C-page 450 Preliminary © 2007 Microchip Technology Inc.
FIGURE 27-22: A/D CONVERSION TIMING
TABLE 27-25: A/D CONVERSION REQUIREMENTS
131
130
132
BSF ADCON0, GO
Q4
A/D CLK
(1)
A/D DATA
ADRES
ADIF
GO
SAMPLE
OLD_DATA
SAMPLING STOPPED
DONE
NEW_DATA
(Note 2)
987 21 0
Note 1: If the A/D clock source is selected as RC, a time of T
CY is added before the A/D clock starts.
This allows the SLEEP instruction to be executed.
2: This is a minimal RC delay (typically 100 ns), which also disconnects the holding capacitor from the analog input.
. . .
. . .
TCY
Param
No.
Symbol Characteristic Min Max Units Conditions
130 T
AD A/D Clock Period PIC18FXXXX 0.7 25.0
(1)
μsTOSC based, VREF ≥ 3.0V
PIC18LFXXXX 1.4 25.0
(1)
μsVDD = 2.0V;
T
OSC based, VREF full range
PIC18FXXXX — 1 μs A/D RC mode
PIC18LFXXXX — 3 μsV
DD = 2.0V; A/D RC mode
131 TCNV Conversion Time
(not including acquisition time) (Note 2)
11 12 TAD
132 TACQ Acquisition Time (Note 3) 1.4 — μs-40°C to +85°C
135 T
SWC Switching Time from Convert → Sample — (Note 4)
136 T
AMP Amplifier Settling Time (Note 5) 1—μs This may be used if the “new” input
voltage has not changed by more
than 1 LSb (i.e., 5 mV @ 5.12V)
from the last sampled voltage (as
stated on C
HOLD).
Note 1: The time of the A/D clock period is dependent on the device frequency and the TAD clock divider.
2: ADRES register may be read on the following TCY cycle.
3: The time for the holding capacitor to acquire the “New” input voltage when the voltage changes full scale
after the conversion (AV
DD to AVSS or AVSS to AVDD). The source impedance ( RS ) on the input channels is
50Ω.
4: On the following cycle of the device clock.
5: See Section 19.0 “10-Bit Analog-to-Digital Converter (A/D) Module” for minimum conditions when input
voltage has changed more than 1 LSb.