Datasheet

PIC18F6525/6621/8525/8621
DS39612C-page 236  2003-2013 Microchip Technology Inc.
The analog reference voltage is software selectable to
either the device’s positive and negative supply voltage
(VDD and VSS), or the voltage level on the RA3/AN3/
V
REF+ pin and RA2/AN2/VREF- pin.
The A/D converter has a unique feature of being able
to operate while the device is in Sleep mode. To
operate in Sleep, the A/D conversion clock must be
derived from the A/D’s internal RC oscillator.
The output of the sample and hold is the input into the
converter which generates the result via successive
approximation.
A device Reset forces all registers to their Reset state.
This forces the A/D module to be turned off and any
conversion is aborted.
Each port pin associated with the A/D converter can be
configured as an analog input (RA3 can also be a
voltage reference), or as a digital I/O. The ADRESH
and ADRESL registers contain the result of the A/D
conversion. When the A/D conversion is complete, the
result is loaded into the ADRESH/ADRESL registers,
the GO/DONE
bit (ADCON0 register) is cleared and A/D
interrupt flag bit, ADIF, is set. The block diagram of the
A/D module is shown in Figure 20-1.
FIGURE 20-1: A/D BLOCK DIAGRAM
(Input Voltage)
V
AIN
VREF+
Reference
Voltage
AV
DD
VCFG1:VCFG0
CHS3:CHS0
AN7
AN6
AN5
AN4
AN3
AN2
AN1
AN0
0111
0110
0101
0100
0011
0010
0001
0000
10-bit
Converter
VREF-
AVSS
A/D
AN15
(1)
AN14
(1)
AN13
(1)
AN12
(1)
AN11
AN10
AN9
AN8
1111
1110
1101
1100
1011
1010
1001
1000
Note 1: Channels AN15 through AN12 are not available on PIC18F6525/6621 devices.
2: I/O pins have diode protection to V
DD and VSS.