Application Notes | Cross-Industry | General Purpose Products | NVRAM | Timekeepers

Second source for 'Snaphat' by using a dual footprint

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AN1019 APPLICATION NOTE
Second Source for "SNAPHAT" by Using a Dual Footprint

By integrating a battery and power switching circuitry in its ZEROPOWER memory devices, STMicroelectronics was the first to develop non-volatile CMOS Static RAM technology. This is conventional, high speed, low power, random access, read/write memory that retains its data even when the external power is removed. By further integrating a crystal oscillator a real time clock in the package for its TIMEKEEPER products, STMicroelectronics provides, in a single chip package, non-volatile SRAM and timekeeping that continues to run without external power. STMicroelectronics has subsequently extended the technique to work with surface mount packaging, in a product range that is known as the SNAPHAT (as shown in Figure 1). The standard 28-pin or 44-pin SOIC allow s the SNAPHAT (containing the battery and crystal) to be mounted on top of the SOIC package after completion of the surface mount process, thereby avoiding these components from being exposed to the high temperatures of the surface-mounting process. Figure 1. SOIC and SNAPHAT Package

AI02493

STMicroelectronics is proud of this technology. The SNAPHAT assembly process is fully automated (as described in AN928), and consistently produces a highly reliable product in volume. This automated equipment takes advantage of microcomputer controlled robotics to obtain the reproducible accuracy required to pick, place, weld and encapsulate both battery and crystal in the SNAPHAT package. However, although we are proud to be the industry's sole source of this technology, we recognise that many customers will be unable to take advantage of it unless we can also provide a path to a second source. Thus, a recommended dual footprint has been designed, and is shown in Figure 2, on the next page. This suggested board layout uses a Dallas Semiconductor hybrid surface mount device in order to provide an alternative for the M48T58, M48T59 or M48T35. Traces have been laid out on a single level with a minimum width and space of 6 mils.

December 1998

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AN1019 - APPLICATION NOTE
Figure 2. Dual Footprint for the Dallas Semiconductor Hybrid Device and the ST ZEROPOWER or TIMEKEEPER SNAPHAT Device
SNAPHAT SOLUTION

A14 A13 VCC W G E DQ7 DQ6 DQ5 DQ4 DQ3 DQ2 DQ1 DQ0 VSS HYBRID SURFACE MOUNT SOLUTION
AI02518

A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0

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AN1019 - APPLICATION NOTE

If you have any questions or suggestions concerning the matters raised in this document, please send them to the following electronic mail addresses:

apps.nvram@ st.com ask.memory@ st.com

(for application support) (for general enquiries)

Please remember to include your name, company, location, telephone number and fax number.

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. 1998 STMicroelectronics - All Rights Reserved The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners. STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands - Singapore Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. http://www.st.com

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Document Number: 6394



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