UPD78F9222MC(T)-5A4-A NEC, UPD78F9222MC(T)-5A4-A Datasheet - Page 176

• Manufacturer Part Number: UPD78F9222MC(T)-5A4-A
• Description: 8BIT MCU, 4K FLASH, 256B RAM, 78F9222
• Manufacturer: NEC

Specifications of UPD78F9222MC(T)-5A4-A

• Controller Family/series: UPD78
• No. Of I/o's: 17
• Ram Memory Size: 256Byte
• Cpu Speed: 10MHz
• No. Of Timers: 4
• No. Of: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 4KB
• Oscillator Type: External, Internal

(4) Noise countermeasures
(5) ANI0/P20 to ANI3/P23
(6) Input impedance of ANI0 to ANI3 pins
176
To maintain the 10-bit resolution, attention must be paid to noise input to the AV
<1> Connect a capacitor with a low equivalent resistance and a high frequency response to the power supply.
<2> Because the effect increases in proportion to the output impedance of the analog input source, it is
<3> Do not switch the A/D conversion function of the ANI0 to ANI3 pins to their alternate functions during
<4> The conversion accuracy can be improved by setting HALT mode immediately after the conversion starts.
Reference
<1> The analog input pins (ANI0 to ANI3) are also used as I/O port pins (P20 to P23).
<2> If a digital pulse is applied to the pins adjacent to the pins currently used for A/D conversion, the expected
In this A/D converter, the internal sampling capacitor is charged and sampling is performed during sampling time.
Since only the leakage current flows other than during sampling and the current for charging the capacitor also
flows during sampling, the input impedance fluctuates both during sampling and otherwise.
If the shortest conversion time of the reference voltage is used, to perform sufficient sampling, it is recommended
to make the output impedance of the analog input source 1 kΩ or lower, or attach a capacitor of around 0.01
to 0.1
C = 0.01 to 0.1 F
voltage
input
recommended that a capacitor be connected externally, as shown in Figure 9-19, to reduce noise.
conversion.
When A/D conversion is performed with any of ANI0 to ANI3 selected, do not access P20 to P23 while
conversion is in progress; otherwise the conversion resolution may be degraded.
value of the A/D conversion may not be obtained due to coupling noise. Therefore, do not apply a pulse to
the pins adjacent to the pin undergoing A/D conversion.
µ
F to the ANI0 to ANI3 pins (see Figure 10-19).
µ
Figure 10-19. Analog Input Pin Connection
CHAPTER 10 A/D CONVERTER
User’s Manual U16898EJ5V0UD
AV
V
ANI0 to ANI3
SS
REF
If there is a possibility that noise equal to or higher than AV
equal to or lower than V
small V
F
value (0.3 V or lower).
SS
may enter, clamp with a diode with a
REF
pin and ANI0 to ANI3 pins.
REF
or
µ
F