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 APPLICATION 

NOTE 

RL78/G14 

R01AN1876EC0100

Rev. 1.00

Feb. 28, 2014

Recommended PCB Layout for Reducing Noise 

Introduction 

The purpose of this document is to help the user understand how to design a good PCB layout with high reducing noise 
performance. A thorough system evaluation is necessary after taking the countermeasures mentioned in this document. 

This document provides an explanation using RL78/G14 sample boards. 

 

Target Device 

RL78/G14 

 

The test results are applied to the following conditions: 

•

 

MCU: RL78/G14 

64-pin 

•

 

PCB type:    Single-side printed board without a polygon 

 

R01AN1876EC0100  Rev. 1.00 

 

Page 1 of 14 

Feb. 28, 2014 

 

Summary of Contents for RL78G14

Page 1: ...with high reducing noise performance A thorough system evaluation is necessary after taking the countermeasures mentioned in this document This document provides an explanation using RL78 G14 sample...

Page 2: ...3 Differences between Recommended Layout and Non recommended Layout 6 3 3 1 Wiring of VDD and VSS 6 3 3 2 Oscillator Concerns 6 3 3 3 Bypass Capacitor 6 3 3 4 Wiring of RESET Pin 7 3 3 5 Wiring of REG...

Page 3: ...t to achieve high reducing noise performance The countermeasures of recommended PCB layout are shown in this application note And the AC line noise contrast test with two types of PCB layout boards is...

Page 4: ...scillator from the VSS wiring for the other peripherals 2 3 Bypass Capacitor Place the bypass capacitor between VSS wiring and VDD wiring close to the MCU And make power supply wiring connect to the M...

Page 5: ...ended layout and the non recommended one are designed with the same schematics Figure 3 1 shows the schematics of the circuits around the MCU Figure 3 1 Schematics of the Circuits around the MCU 3 2 P...

Page 6: ...Oscillator circuits X1 C1 and C2 on the recommended board are closer to the MCU than the non recommended one The wiring from oscillator circuit to the MCU on the recommended board is shorter than the...

Page 7: ...pacitor C4 Reason The long wiring between C3 and the MCU REGC pin may become a noise antenna The REGC should be connected to VSS wiring after the bypass capacitor otherwise the bypass capacitor effect...

Page 8: ...sec Note The red LEDs are controlled by the main loop and the yellow LEDs are controlled by the interrupt handler The red and yellow LEDs blink synchronously System initialization Interrupt initializ...

Page 9: ...ink synchronously The MCU status can be evaluated by observing these LEDs If the MCU operates normally within 1 minute the result is considered good and the table is filled with a If the MCU generates...

Page 10: ...3600 3 3 3500 3 3 3400 3 3 3300 3 3 3200 3 3 3100 3 3 3000 3 3 2900 3 3 2800 3 3 2700 3 3 2600 3 3 2500 3 3 2400 3 2300 3 2200 2100 2000 Polarity Voltage Note Voltage Noise value Unit V higher value...

Page 11: ...one is below 2500 V Conclusions from this test are as follows Higher reducing noise performance can be achieved by designing a PCB layout according to the recommendations Due to the high reducing nois...

Page 12: ...uit to modify the VSS connection Refer to the red section in Figure 5 1 Oscillator concerns Cutoff the original wiring which connects the VSS of oscillator circuit to the MCU VSS pin Connect them with...

Page 13: ...he non recommended board the results of reducing noise performance improved drastically But when developing a product the PCB should be redesigned according to the recommended layout Note the followin...

Page 14: ...Software R01US0015EJ The latest versions can be downloaded from the Renesas Electronics website Technical Updates Technical News The latest information can be downloaded from the Renesas Electronics...

Page 15: ...A 1 Revision History Description Rev Date Page Summary 1 00 Feb 28 2014 First edition issued...

Page 16: ...unction are not guaranteed from the moment when power is supplied until the power reaches the level at which resetting has been specified 3 Prohibition of Access to Reserved Addresses Access to reserv...

Page 17: ...nd malfunction prevention appropriate treatment for aging degradation or any other appropriate measures Because the evaluation of microcomputer software alone is very difficult please evaluate the saf...

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