Choosing Atmel ATF150xASV(L) POR Options Summary Atmel EPLDs are capable of operation down to the reset level, VRST. In 5.0V devices, VRST generally is midway between the specified minimum power supply voltage and 0.0V, and so the margin for droop, noise, etc. is sufficient. In low voltage devices, VRST is generally just below the specified minimum power supply voltage, and available margin is reduced. In applications where the supply voltage falls close to the specified minimum power supply voltage, Atmel recommends increasing the margin for falling V CC . In the ATF150xASV(L) family, Atmel recommends changing the Power_On_Reset hysteresis from small to large. Methods and means of implementing this recommendation are discussed. Details EPLD Technical Bulletin All Atmel EPLDs are designed with a power-up reset function to initialize all registers at a point delayed slightly from V CC rising above V RST. Similarly, if VCC falls below VRST, the device will return to the reset state. Due to the asynchronous nature of reset and uncertainty of how VCC actually rises in the system, the following conditions are required: 1. The VCC rise must be monotonic. 2. After reset occurs, all input and feedback setup times must be met before driving the clock pin high. 3. The clock must remain stable during TD. The Atmel ATF150xASV family of 3.3V parts offers the user a programmable option for the hysteresis about the reset level, small or large. In the case of the Atmel ATF150xASV family, nominal VCC is 3.3V, the minimum VCC is 3.0V and the default small hysteresis choice puts the VRST level just below minimum VCC for both rising and falling VCC. To ensure a robust operating environment in these cases, Atmel recommends that users set the power-up reset hysteresis to large. With the large hysteresis option selected, the reset level for falling VCC drops to a lower level, increasing the margin before the device returns to the reset state. * Synario users should open the Properties dialog box and change setting of the Power_On_Reset Hysteresis from the default "Small" to "Large" before running the Fitting process. * Atmel POF2JED users should include the flag "-power_reset" on the command line after "filename.POF" when running conversions. To ensure that the registers are properly re-initialized when VCC rises again, the following condition is added: 4. If VCC falls below 2.0V, it must shut off completely before the device is turned on again. With the hysteresis option set to large, ICC is reduced several hundred A. This is especially significant for the "ATF150xASL" versions because it brings the standby ICC down to the A level. Rev. 1964A-10/00 1 Atmel Headquarters Atmel Operations Corporate Headquarters Atmel Colorado Springs 2325 Orchard Parkway San Jose, CA 95131 TEL (408) 441-0311 FAX (408) 487-2600 Europe 1150 E. Cheyenne Mtn. Blvd. Colorado Springs, CO 80906 TEL (719) 576-3300 FAX (719) 540-1759 Atmel Rousset Atmel SarL Route des Arsenaux 41 Casa Postale 80 CH-1705 Fribourg Switzerland TEL (41) 26-426-5555 FAX (41) 26-426-5500 Asia Atmel Asia, Ltd. Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimhatsui East Kowloon Hong Kong TEL (852) 2721-9778 FAX (852) 2722-1369 Japan Zone Industrielle 13106 Rousset Cedex France TEL (33) 4-4253-6000 FAX (33) 4-4253-6001 Atmel Smart Card ICs Scottish Enterprise Technology Park East Kilbride, Scotland G75 0QR TEL (44) 1355-803-000 FAX (44) 1355-242-743 Atmel Grenoble Avenue de Rochepleine BP 123 38521 Saint-Egreve Cedex France TEL (33) 4-7658-3000 FAX (33) 4-7658-3480 Atmel Japan K.K. 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan TEL (81) 3-3523-3551 FAX (81) 3-3523-7581 Atmel EPLD Hotline Fax-on-Demand 1-(408) 436-4333 North America: 1-(800) 292-8635 Atmel EPLD e-mail International: 1-(408) 441-0732 pld@atmel.com Atmel EPLD Fax e-mail 1-(408) 487-2664 literature@atmel.com Web Site http://www.atmel.com BBS 1-(408) 436-4309 (c) Atmel Corporation 2000. Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company's standard warranty which is detailed in Atmel's Terms and Conditions located on the Company's web site. The Company assumes no responsibility for any errors which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are granted by the Company in connection with the sale of Atmel products, expressly or by implication. Atmel's products are not authorized for use as critical components in life suppor t devices or systems. Marks bearing (R) and/or TM are registered trademarks and trademarks of Atmel Corporation. Printed on recycled paper. Terms and product names in this document may be trademarks of others. 1964A-10/00/xM