PIC18F2458 Datasheet, PDF (24/46 Pages) Microchip Technology – 28/40/44-Pin High-Performance, Enhanced Flash, USB Microcontrollers with 12-Bit A/D and nanoWatt Technology

PIC18F2458/2553/4458/4553
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/
VREF+ and RA2/AN2/VREF-/CVREF pins.
The A/D Converter has a unique feature of being able
to operate while the device is in Sleep mode. To oper-
ate 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 in progress is aborted.
Each port pin associated with the A/D Converter can be
configured as an analog input 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 com-
plete, the result is loaded into the ADRESH:ADRESL
register pair, the GO/DONE bit (ADCON0 register) is
cleared and the A/D Interrupt Flag bit, ADIF, is set. The
block diagram of the A/D module is shown in Figure 2-1.
FIGURE 2-1:
A/D BLOCK DIAGRAM
CHS3:CHS0
1100
1011
1010
1001
1000
0111
0110
0101
12-Bit
A/D
Converter
VAIN
(Input Voltage)
0100
0011
0010
Reference
Voltage
VCFG1:VCFG0
VREF+
VREF-
VDD
X0
X1
1X
0X
VSS
0001
0000
AN12
AN11
AN10
AN9
AN8
AN7⁽¹⁾
AN6⁽¹⁾
AN5⁽¹⁾
AN4
AN3
AN2
AN1
AN0
Note 1: Channels AN5 through AN7 are not available on 28-pin devices.
DS39887B-page 22
Preliminary
© 2007 Microchip Technology Inc.