Connection Of A Bypass Capacitor Across; Ss Cc; Ss Line And V Cc Line; Fig.6.4.5 Bypass Capacitor Across V - Renesas 7200 Series User Manual

6.4.2 Connection of a bypass capacitor across

V line and V
SS CC
Connect an approximately 0.1 µ F bypass capacitor
across the V line and the V
SS
Connect a bypass capacitor across the V
and the V pin at equal length.
CC
Connect a bypass capacitor across the V
and the V pin with the shortest possible wiring.
CC
Use lines with a larger diameter than other signal
lines for V line and V
SS
6.4.3 Wiring to analog input pins
Connect an approximately 100 Ω to 1 kΩ resistor
to an analog signal line which is connected to an
analog input pin in series. Besides, connect the
resistor to the microcomputer as close as possible.
Connect an approximately 1000 pF capacitor across
the V pin and the analog input pin. Besides,
SS
connect the capacitor to the V
possible. Also, connect the capacitor across the
analog input pin and the V
Reason
Signals which is input in an analog input pin (such
as an A-D converter/comparator input pin) are usually
output signals from sensor. The sensor which detects
a change of event is installed far from the printed
circuit board with a microcomputer, the wiring to an
analog input pin is longer necessarily. This long
wiring functions as an antenna which feeds noise
into the microcomputer, which causes noise to an
analog input pin.
If a capacitor between an analog input pin and the
V pin is grounded at a position far away from the
SS
V pin, noise on the GND line may enter a
SS
microcomputer through the capacitor.
line
line as follows:
CC
SS
SS
line.
CC
pin as close as
SS
pin at equal length.
SS
7220 Group User's Manual
6.4 Countermeasures against noise
pin
pin

Fig.6.4.5 Bypass capacitor across V

V line
CC
Noise
Thermistor
Note : The resistor is used for dividing

Fig.6.4.6 Analog signal line and resistor and capacitor

APPENDIX
Chip
V V
CC SS
(Note)
Microcomputer
Analog
input pin
O.K.
N.G.
V
SS
resistance with a thermistor.
line and
SS
6-13