ST AN1019 Application note

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 techno logy. 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
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

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STMicroelectronics is proud of this technology. The SNAPHA T assembly process is fully automated (as
described in
equipment takes advantage of microcomputer controlled robotics to obtain the reproducib le accurac y 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 designe d, 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 M48 T58, M48T 59 or M48T35. T races have be en laid out on a single level
with a minimum width and space of 6 mils.

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), and consistently produces a highly reliable product in volume. This automated

AN1019 - APPLICATION NOTE

Figure 2. Dual Footprint for the D allas Sem icon du ctor Hybrid Device an d th e S T ZER OP OWER o r
TIMEKEEPER SNAPHAT Device

SNAPHAT SOLUTION

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SS

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HYBRID SURFACE MOUNT SOLUTION

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