UPD78F9418AGK-9EU Renesas Electronics America, UPD78F9418AGK-9EU Datasheet - Page 166

• Manufacturer Part Number: UPD78F9418AGK-9EU
• Manufacturer: Renesas Electronics America

Specifications of UPD78F9418AGK-9EU

• Lead Free Status / Rohs Status: Supplier Unconfirmed

164
(7)
(8)
(9)
ANI0 to ANI6
The analog input pins (ANI0 to ANI6) are alternate-function pins. They are also used as port pins (P60 to
P66).
If any of ANI0 to ANI6 has been selected for A/D conversion, do not execute input instructions for the ports.
Otherwise, the conversion resolution may become lower.
If a digital pulse is applied to a pin adjacent to the analog input pins during A/D conversion, coupling noise
may occur which prevents an A/D conversion result from being attained as expected. Avoid applying a digital
pulse to pins adjacent to the analog input pins during A/D conversion.
Input impedance of ANI0 to ANI6 pins
This A/D converter charges the internal sampling capacitor for about 1/10 of the conversion time, and
performs sampling.
Therefore at times other than sampling, only the leak current is output. During sampling, the current for
charging the capacitor is also output, so the input impedance fluctuates and has no meaning.
However, to ensure adequate sampling, it is recommended that the output impedance of the analog input
source be set to below 10 k , or a 100 pF capacitor be connected to the ANI0 to ANI6 pins (see Figure 11-
10).
Input impedance of the AV
A series resistor string of 10 k is connected across the AV
If the output impedance of the reference voltage source is high, this high impedance is eventually connected
in parallel with the series resistor string across the AV
voltage error.
Reference voltage
input
C = 100 to 1000 pF
CHAPTER 11 10-BIT A/D CONVERTER ( PD789417A SUBSERIES)
Figure 11-10. Analog Input Pin Processing
REF
pin
User’s Manual U13952EJ3V1UD
If noise greater than AV
AV
the voltage at the pin by attaching a diode with
a small V
AV
V
AV
AV
V
REF
SS
DD0
SS0
REF
DD
SS
REF
is likely to come to the AV
and AV
and AV
F
(0.3 V or lower).
SS
SS
pins, leading to a higher reference
pins.
REF
or less than
REF
pin, clamp