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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 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
AI02493
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.
December 1998 1/3
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), and consistently produces a highly reliable product in volume. This automated
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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
A14
A13
V
CC
W
G
E
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DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
V
SS
A12
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A10
A9
A8
A7
A6
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A0
HYBRID SURFACE MOUNT SOLUTION
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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
Please remember to include your name, company, location, telephone num ber and fax number.
(for application support)
(for general enquiries)
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 implic ation or o th erwise un der any pat ent or patent right s of STMi croelectr oni cs. Specifications menti oned in th i s publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as c ritical components in li fe support devices or syst em s without express wri t ten approval of STMic roelectronics.
© 1998 STMicroelectronics - All Rights Reserved
The ST logo is a registered tradem ark of STMicroelectronics.
All other na m es are the property of the i r respectiv e owners.
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