Datasheet

 2010 Microchip Technology Inc. Preliminary DS39974A-page 373
PIC18F47J13 FAMILY
After the A/D module has been configured as desired,
the selected channel must be acquired before the
conversion is started. The analog input channels must
have their corresponding TRIS bits selected as inputs.
To determine acquisition time, see Section 22.1 “A/D
Acquisition Requirements”. After this acquisition
time has elapsed, the A/D conversion can be started.
An acquisition time can be programmed to occur
between setting the GO/DONE
bit and the actual start
of the conversion.
The following steps should be followed to do an A/D
conversion:
1. Configure the A/D module:
• Configure the required ADC pins as analog
pins using ANCON0, ANCON1
• Set voltage reference using ADCON0
• Select A/D input channel (ADCON0)
• Select A/D acquisition time (ADCON1)
• Select A/D conversion clock (ADCON1)
• Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE bit
•Set GIE bit
3. Wait the required acquisition time (if required).
4. Start conversion:
• Set GO/DONE
bit (ADCON0<1>)
5. Wait for A/D conversion to complete, by either:
• Polling for the GO/DONE
bit to be cleared
OR
• Waiting for the A/D interrupt
6. Read A/D Result registers (ADRESH:ADRESL);
clear bit, ADIF, if required.
7. For the next conversion, go to Step 1 or Step 2,
as required. The A/D conversion time per bit is
defined as T
AD. A minimum Wait of 2 TAD is
required before the next acquisition starts.
FIGURE 22-2: ANALOG INPUT MODEL
VAIN
CPIN
RS
ANx
5 pF
V
DD
VT = 0.6V
V
T = 0.6V
I
LEAKAGE
RIC 1k
Sampling
Switch
SS
R
SS
CHOLD = 25 pF
V
SS
Sampling Switch
1234
(k)
VDD
±100 nA
Legend: CPIN
VT
ILEAKAGE
RIC
SS
C
HOLD
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to
= Interconnect Resistance
= Sampling Switch
= Sample/Hold Capacitance (from DAC)
various junctions
= Sampling Switch ResistanceRSS