AN1019 STMICROELECTRONICS | Alldatasheet

Document overview

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Technical content

Second source for SNAPHAT® using a dual footprint Introduction 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 and 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: "SOIC and SNAPHAT® package" ). The standard 28-pin or 44-pin SOIC allows 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

1 Overview

The SNAPHAT® assembly process is fully automated 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 recognize 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: "Dual footprint for the Maxim Integrated hybrid device and the ST ZEROPOWER® or TIMEKEEPER SNAPHAT® device" . This suggested board layout uses a Maximum Integrated hybrid surface mount device in order to provide an alternative for the M48T58/Y, M48T59, M48T35/Y, or M48T35AV. Traces have been laid out on a single level with a minimum width and space of 6 mils. Figure 2: Dual footprint for the Maxim Integrated hybrid device and the ST ZEROPOWER® or TIMEKEEPER SNAPHAT® device VCC AI02518 W G E DQ7 DQ6 DQ5 DQ4 DQ3 DQ2 DQ1 DQ0 VSS A12 A11 A10 A13 A14 HYBRID SURFACE MOUNT SOLUTION SNAPHAT SOLUTION

2 Revision history

Table 1: Document revision history Date Version Change Dec-1998 1 Initial release 01-Nov-2013 2 Textual updates; revised document presentation