Microchip Technology IC PIC MCU PIC18F65J15-I/PT TQFP-64 MCP PIC18F65J15-I/PT Data Sheet

© 2009 Microchip Technology Inc.

DS39663F-page 265

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 an
input. To determine acquisition time, see Section 21.1
“A/D Acquisition Requirements”. After this acquisi-
tion 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 analog pins, voltage reference and 

digital I/O (ADCON1)

• Select A/D input channel (ADCON0)
• Select A/D acquisition time (ADCON2)
• Select A/D conversion clock (ADCON2)
• 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 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 T

AD

 is

required before next acquisition starts.

V

AIN

C

PIN

R

S

ANx

5 pF

V

DD

V

T

 = 0.6V

V

T

 = 0.6V

I

LEAKAGE

R

IC

 ≤ 1k

Sampling
Switch

SS

R

SS

C

HOLD

 = 25 pF

V

SS

6V

Sampling Switch

5V
4V
3V
2V

1

2

3

4

(k

Ω)

V

DD

±100 nA

Legend: C

PIN

V

T

I

LEAKAGE

R

IC

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 Resistance

R

SS