Datasheet

78K0/Kx2-L CHAPTER 12 A/D CONVERTER
R01UH0028EJ0400 Rev.4.00 403
Sep 27, 2010
12.2 Configuration of A/D Converter
The A/D converter includes the following hardware.
(1) ANI0 to ANI10 pins
These are the analog input pins of the 11-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 can be used as I/O port pins.
Remark A/D converter analog input pins differ depending on products.
• 78K0/KY2-L: ANI0 to ANI3
• 78K0/KA2-L (20-pin products): ANI0 to ANI5
• 78K0/KA2-L (25-pin products): ANI0 to ANI6
• 78K0/KA2-L (32-pin products): ANI0 to ANI10
• 78K0/KB2-L: ANI0 to ANI3, ANI8 to ANI10
• 78K0/KC2-L (40-pin product): ANI0 to ANI6, ANI8 to ANI10
• 78K0/KC2-L (44-pin and 48-pin products): ANI0 to ANI10
(2) AMP0OUT pin (products with operational amplifier only)
AMP0OUT is the output pin of operational amplifier 0.
This functions alternately as ANI1. The A/D converter can perform A/D conversion by selecting the output signal of
operational amplifier 0 as the analog input source.
(3) AMP1OUT pin (products with operational amplifier of 78K0/KB2-L and 78K0/KC2-L only)
AMP1OUT is the output pin of operational amplifier 1.
This functions alternately as ANI9. The A/D converter can perform A/D conversion by selecting the output signal of
operational amplifier 1 as the analog input source.
(4) PGAOUT signal (products with operational amplifier only)
PGAOUT is the output signal of PGA.
The A/D converter can perform A/D conversion by selecting the output signal of PGA as the analog input source.
(5) Sample & hold circuit
The sample & hold circuit samples each of the analog input voltages sequentially sent from the input circuit, and
sends them to the A/D voltage comparator. This circuit also holds the sampled analog input voltage during A/D
conversion.
(6) Comparison voltage generator
The comparison voltage generator is connected between AV
REF and AVSS, and generates a voltage to be compared
with an analog input. The operation of the comparison voltage generator is enabled or disabled by using the ADCS
bit (bit 7 of the ADM0 register). The power consumption can be reduced by stopping the operation of the comparison
voltage generator when A/D conversion is not performed.
(7) A/D voltage comparator
The A/D voltage comparator compares the sampled voltage values with the output voltage of the comparison voltage
generator. The operation of the A/D voltage comparator is enabled or disabled by using the ADCE bit (bit 0 of the
ADM0 register). The power consumption can be reduced by stopping the operation of the A/D voltage comparator
when A/D conversion is not performed.
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