APPLICATION NOTES. Electrical Fast Transient (EFT) Noise Test Solution ELAN MICROELECTRONICS CORP.

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1 Electrical Fast Transient (EFT) Noise Test Solution APPLICATION NOTES ELAN MICROELECTRONICS CORP. Document Number : AN-025 Date of Issue : March 2007 Issue Version : 1.0 Supported Chips : OTP Type: EM78P341N Series, EM78P343N Series, EM78P320N, EM78P330N, EM78P510N, EM78P220N Series, EM78P159N, EM78P154N Flash Type EM78F651N EM78F652N Applicable Software :

2 Trademark Acknowledgments: IBM is a registered trademark and PS/2 is a trademark of IBM Windows is a trademark of Microsoft Corporation ELAN and ELAN logo are trademarks of ELAN Microelectronics Corporation Copyright 2007 by ELAN Microelectronics Corporation All Rights Reserved Printed in Taiwan The contents of this Handbook (publication) are subject to change without further notice. ELAN Microelectronics assumes no responsibility concerning the accuracy, adequacy, or completeness of this publication. ELAN Microelectronics makes no commitment to update, or to keep current the information and material contained in this publication. Such information and material may change to conform to each confirmed order. In no event shall ELAN Microelectronics be made responsible for any claims attributed to errors, omissions, or other inaccuracies in the information or material contained in this publication. ELAN Microelectronics shall not be liable for direct, indirect, special incidental, or consequential damages arising from the use of such information or material. The software (if any) described in this publication is furnished under a license or nondisclosure agreement, and may be used or copied only in accordance with the terms of such agreement. ELAN Microelectronics products are not intended for use in life support appliances, devices, or systems. Use of ELAN Microelectronics product in such applications is not supported and is prohibited. NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS WITHOUT THE EXPRESSED WRITTEN PERMISSION OF ELAN MICROELECTRONICS. ELAN MICROELECTRONICS CORPORATION Headquarters: No. 12, Innovation Road 1 Hsinchu Science Park Hsinchu, Taiwan Tel: Fax: Hong Kong: Elan (HK) Microelectronics Corporation, Ltd. Flat A, 19/F, World Tech Centre 95 How Ming Street, Kwun Tong Kowloon, HONG KONG Tel: Fax: elanhk@emc.com.hk Shenzhen: Elan Microelectronics Shenzhen, Ltd. SSMEC Bldg., 3F, Gaoxin S. Ave. Shenzhen Hi-Tech Industrial Park Shenzhen, Guandong, CHINA Tel: Fax: USA: Elan Information Technology Group (USA) 1821 Saratoga Ave., Suite 250 Saratoga, CA USA Tel: Fax: Shanghai: Elan Microelectronics Shanghai, Ltd. 23/Bldg. #115 Lane 572, Bibo Road Zhangjiang Hi-Tech Park Shanghai, CHINA Tel: Fax:

3 Contents 1 Gene neral Description 1 2 Underlying Reason 2 3 Solution 3 Application Notes for EFT Noise Test Solution iii

4 Reference Manual Revision History Doc. Version Revision Description Date 1.0 Initial Official Release Version 2007/03/02 iv Application Notes for EFT Noise Test Solution

5 1 General Description Electrical Fast Transients (EFT) are caused by transient currents (commonly called arcing) during a make or break of contact. In system application of Elan s 8-bit MCU IC, some errors may occur, i.e., abnormal reset, during EFT testing at special cases particularly at an amplitude of 4KV and 2.5kHz frequency. This could be due to some timing conflicts. Hence, this application note is intended to assist users by giving suggestions on practical design techniques that provide cost-effective protection for electrical fast transients (EFT). Electronic products are tested for EFT immunity to ensure their reliability if subjected to some levels of fast transients. The devices supported by this application notes are listed below: OTP Type: EM78P341N Series, EM78P343N Series, EM78P320N, EM78P330N, EM78P510N, EM78P220N Series, EM78P159N, EM78P154N Flash Type: EM78F651N, EM78F652N Application Notes for EFT Noise Test Solution 1

6 2 Underlying Reason MCU Immunity performance is classified into four categories, namely from Class A to D. Class B is a temporary degradation or loss of performance or function which is self recoverable after the transient is removed. Another form of MCU performance degradation is a reset. In the design implementation of these devices, it is necessary to take approximately 500µs to make sure the system is stable, with WDT prescaler=1:1 in this case. As shown in Fig. 1, EFT input =2.5kHz, the period of each burst A =400µs, and the WDT time-out period B is 500µs. Thus, the EFT test result may fail or go to class B since inside the burst insert time (400µs* 75=30ms), sometimes reset timing may be reached. A=400us B EFT Insert Figure 1 EFT Test Timing Diagram 2 Application Notes for EFT Noise Test Solution

7 3 Solution There are two ways to avoid this phenomenon to occur. a. The prescaler (PSWE, PSW [2..0] inside WDT Control Register) value should not be set less than 1:4 (1:4, 1:8, 1:16 and so on). For example: If the prescaler value is set as 1:4, then the WDT timeout will be 72ms (more than 30ms) and so, this will be safe in the test. b. Just set the WDT as disabled in the code option to avoid a reset to occur This solution is just used to avoid EFT fail test to occur. In the real system, the WDT time may still be set as per requirement. Application Notes for EFT Noise Test Solution 3

Product Specification

EASY SOUND EM55000S Series Product Specification DOC. VERSION 1.2 ELAN MICROELECTRONICS CORP. January 2005 Trademark Acknowledgments: IBM is a registered trademark and PS/2 is a trademark of IBM. Windows