CHAPTER 10 A/D CONVERTER
User’s Manual U17446EJ3V1UD
162
Figure 10-2 shows the block diagram of A/D converter.
Figure 10-2. Block Diagram of A/D Converter
AV
REF
AV
SS
INTAD
2
ADS1
ADS0
AV
SS
ANI0/P20
ANI1/P21
ANI2/P22
ANI3/P23
ADCS
FR2
FR1
ADCE
FR0
3
Sample & hold circuit
Voltage comparator
Controller
A/D conversion result register
(ADCR, ADCRH)
Analog input
channel specification
register (ADS)
A/D converter mode
register (ADM)
Internal bus
Successive
approximation
register (SAR)
Selector
D/A converter
10.2 Configuration of A/D Converter
The A/D converter consists of the following hardware.
(1) ANI0 to ANI3 pins
These are the analog input pins of the 4-channel A/D converter. They input analog signals to be converted into
digital signals. Pins other than the one selected as the analog input pin by the analog input channel specification
register (ADS) can be used as I/O port pins.
(2) Sample & hold circuit
The sample & hold circuit samples the input signal of the analog input pin selected by the selector when A/D
conversion is started, and holds the sampled analog input voltage value during A/D conversion.
(3) D/A
converter
The D/A converter is connected between AV
REF
and AV
SS
, and generates a voltage to be compared with the
analog input signal.
(4) Voltage
comparator
The voltage comparator compares the sampled analog input voltage and the output voltage of the D/A converter.