Analog Input Pin Disposition - NEC PD78076 User Manual

Pd78078 series; pd78078y series 8-bit single-chip microcontrollers

Table of Contents

(2) Input range of ANI0 to ANI7

The input voltages of ANI0 to ANI7 should be within the specification range. In particular, if a voltage above

that channel will be indeterminate. The conversion values of the other channels may also be affected.

(3) Noise countermeasures

In order to maintain 8-bit resolution, attention must be paid to noise on pins AV

the effect increases in proportion to the output impedance of the analog input source, it is recommended

that a capacitor be connected externally as shown in Figure 15-10 in order to reduce noise.

Voltage Input

(4) Pins ANI0/P10 to ANI7/P17

The analog input pins ANI0 to ANI7 also function as input/output port (PORT1) pins. When A/D conversion

is performed with any of pins ANI0 to ANI7 selected, be sure not to execute an input instruction to PORT

1 while conversion is in progress, as this may reduce the conversion resolution.

Also, if digital pulses are applied to a pin adjacent to the pin in the process of A/D conversion, the expected

A/D conversion value may not be obtainable due to coupling noise. Therefore, avoid applying pulses to pins

adjacent to the pin undergoing A/D conversion.

CHAPTER 15 A/D CONVERTER

is input (even if within the absolute maximum rating range), the conversion value for

Figure 15-10. Analog Input Pin Disposition

If there is possibility that noise whose level is

clamp with a diode with a small V

or higher or AV

or lower may enter,

ANI0 to ANI7

and ANI0 to ANI7. Since

(0.3 V or less).