Table of Contents
Chapter 44 A/D Converter
This chapter provides an overview of the A/D converter, describes the register structure and functions, and
describes the operation of the A/D converter.
•
1. Overview of A/D Converter
•
2. Block Diagram of A/D Converter
•
3. Registers of A/D Converter
• 4. Operation of A/D Converter
1. Overview of A/D Converter
The A/D converter converts analog input voltage into digital values and provides the following features.
Features of A/D converter:
Conversion time: minimum 3 us per channel.
RC type successive approximation conversion with sample & hold circuit
10-bit or 8-bit resolution
Program section analog input from 32 channels
Single conversion mode: conversion of one selected channel
Scan conversion mode: continuous conversion of multiple channels, programmable for up to 32 channels
Single conversion mode:
Continuous mode:
Stop mode:
A/D conversion can be followed by an A/D conversion interrupt request to CPU. This interrupt, an option that
is ideal for continuous processing can be used to start a DMA transfer of the results of A/D conversion to
memory.
Startup may be by software, external trigger (falling edge) or timer (rising edge).
■ Input impedance
Sampling circuit of A/D converter is expressed in
Analog
s ignal
s ourc e
Convert the specified channel only once.
Repeatedly convert the specified channels.
Convert one channel then temporarily halt until the next activation.
(Enables synchronization of the conversion start timing.)
Re xt
ANx
Don•ft set Rext over maximum sampling time (Tsamp).
Re xt = Ts amp/ (7*Cin) - Rin
Figure 1-1 Input Impedance
Figure 1-1 Input Impedance
Rin
13.6kƒ¶ (AVCC•† 4.0V)
2.52kƒ¶ (AVCC•† 4.5V)
Analog S W
Cin:max 10.7pF
Chapter 44 A/D Converter
1.Overview of A/D Converter
ADC
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