CHAPTER 13 A/D CONVERTER
User’s Manual U16896EJ2V0UD
367
(1) ANI0 to ANI7 pins
These are analog input pins for the 8 channels of the A/D converter. They are used to input analog signals to
be converted into digital signals. Pins other than those selected as analog input by the ADS register can be
used as input ports.
(2) Sample & hold circuit
The sample & hold circuit samples the analog input signals selected by the input circuit and sends the
sampled data to the voltage comparator. This circuit holds the sampled analog input voltage during A/D
conversion.
(3) Series resistor string
The series resistor string is connected between AV
REF0
and AV
SS
and generates a voltage for comparison with
the analog input signal.
(4) Voltage
comparator
The voltage comparator compares the value that is sampled and held with the output voltage of the series
resistor string.
(5) Successive approximation register (SAR)
This register compares the sampled analog voltage value with the voltage value from the series resistor string,
and converts the comparison result starting from the most significant bit (MSB).
When the least significant bit (LSB) has been converted to a digital value (end of A/D conversion), the contents
of the SAR register are transferred to the ADCR register.
The SAR register cannot be read or written directly.
(6) A/D conversion result register (ADCR), A/D conversion result register H (ADCRH)
Each time A/D conversion ends, the conversion results are loaded from the successive approximation register
and the results of A/D conversion are held in the higher 10 bits of this register (the lower 6 bits are fixed to 0).
(7) Controller
The controller compares the A/D conversion results (the value of the ADCRH register) with the value of the
PFT register when A/D conversion ends or the power fail detection function is used. It generates INTAD signal
only when the comparison conditions match.
(8) AV
REF0
pin
This is the analog power supply pin/reference voltage input pin of the A/D converter. Always use the same
potential as the V
DD
pin even when not using the A/D converter.
The signals input to the ANI0 to ANI7 pins are converted into digital signals based on the voltage applied
across AV
REF0
and AV
SS
.
(9) AV
SS
pin
This is the ground potential pin of the A/D converter. Always use the same potential as the V
SS
pin even when
not using the A/D converter.
