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RX Family
2.3 Reset Pin
When directly connecting the reset pin to the reset IC, position the reset IC as close as possible. Noise can
also be reduced by inserting a low-pass filter. Do not run the trace for the reset pin parallel to other traces
(traces with large current flows or rapid level changes). If no low-pass filter is used, shield the trace for the
reset pin with the GND trace. The GND traces used for shielding should be at least 0.3 mm wide and there
should be a space of 0.3 mm to 2.0 mm between them and adjacent traces.
Board design hint
The pulse width input to the reset pin is specified in the timing requirements. If the noise input to the
reset pin has a shorter width than the specified pulse width, a reset condition may be released before
the MCU's internal initialization has completed, possibly causing program runaway.
Figure 2.9 shows an example reset pin circuit configuration, and Figure 2.10 shows an example reset pin
wiring pattern (multilayer board).
Reset IC
(RNA51957)
Figure 2.9 Example Reset Pin Circuit Configuration (With Low-Pass Filter)
Reset IC
GND
To GND
To +3.3 V
Through hole
Front side
wiring pattern
Back side
wiring pattern
R01AN1411EJ0110 Rev.1.10
Oct.26.21
OUT
GND
Depending on the specifications
of the reset IC, a pull-up resistor
VCC
may be necessary.
R
OUT
Resistor
R
Run the wiring traces on the
front side if it will not affect the
Capacitor
C
peripheral circuits.
Figure 2.10 Example Reset Pin Wiring Pattern
Hardware Design Guide
RES#
RX Family MCU
VSS
If at all possible place the filter
circuit on the MCU side to avoid
affecting the peripheral circuits.
C
To GND
RX Family
RES#
VSS
Page 14 of 32
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