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Section 23. 10-bit A/D Converter

HIGHLIGHTS
This section of the manual contains the following major topics: 23.1 Introduction ..................................................................................................................23-2 23.2 Control Register ...........................................................................................................23-3 23.3Operation .....................................................................................................................23-5 23.4 A/D Acquisition Requirements .....................................................................................23-6 23.5 Selecting the A/D Conversion Clock ............................................................................23-8 23.6 Configuring Analog PortPins.......................................................................................23-9 23.7 A/D Conversions ........................................................................................................23-10 23.8 Operation During Sleep .............................................................................................23-14 23.9 Effects of aReset.......................................................................................................23-14 23.10 A/D Accuracy/Error ....................................................................................................23-15 23.11 Connection Considerations ........................................................................................23-16 23.12 Transfer Function.......................................................................................................23-16 23.13 Initialization ................................................................................................................23-17 23.14 Design Tips ................................................................................................................23-18 23.15 Related ApplicationNotes..........................................................................................23-19 23.16 Revision History .........................................................................................................23-20

23
10-bit A/D Converter

Note 1: At present NO released mid-range MCU devices are available with this module. Devices are planned, but there is no schedule for availability. Pleaserefer to Microchip’s Web site or BBS for release of Product Briefs which detail the features of devices. If your current design requires a 10-bit A/D, please look at the PIC17C756 which has a 12-channel 10-bit A/D. This A/D has characteristics which are identical to this module’s description.

© 1997 Microchip Technology Inc.

Preliminary

DS31023A page 23-1

PICmicro MID-RANGE MCU FAMILY23.1 Introduction
The analog-to-digital (A/D) converter module can have up to eight analog inputs for a device. The analog input charges a sample and hold capacitor. The output of the sample and hold capacitor is the input into the converter. The converter then generates a digital result of this analog level via successive approximation. This A/D conversion, of the analog input signal, results ina corresponding 10-bit digital number. The analog reference voltages (positive and negative supply) are software selectable to either the device’s supply voltages (AVDD, AVss) or the voltage level on the AN3/VREF+ and AN2/VREFpins. The A/D converter has a unique feature of being able to operate while the device is in SLEEP mode. The A/D module has four registers. These registers are: • • • • A/DResult High Register (ADRESH) A/D Result Low Register (ADRESL) A/D Control Register0 (ADCON0) A/D Control Register1 (ADCON1)

The ADCON0 register, shown in Figure 23-1, controls the operation of the A/D module. The ADCON1 register, shown in Figure 23-2, configures the functions of the port pins. The port pins can be configured as analog inputs (AN3 and AN2 can also be the voltage references) or...