AN1000
Application note
Reduced footprint ZEROPOWER® and TIMEKEEPER® supervisor
surface-mount solution
Introduction
The ZEROPOWER® and TIMEKEEPER® supervisors from STMicroelectronics (such as theM40Z300W and the M48T201V/Y) offer all the advantages of using surface-mounttechnology, and are well suited to automatic assembly-line processes.
Designed to be highly modular, they interface directly with commodity SRAM, and use acommercially available cell for the internal battery (which is easily replaceable). Thesedevices are designed for lower system costs when compared to designs using competitors’
hybrid products.
Moreover, even though the ST products need an external SRAM chip, the footprint of thetwo chips together is still 80% of that of the competitors’ single chip solutions. Figure 1
compares the footprint of a competitor’s chip (not unlike MAXIM/Dallas Semiconductor’s
hybrid surface-mount PowerCap module) with an ST device connected to a 1Mbit (128K x 8)
low power SRAM chip (perhaps from Hitachi, Sony or Samsung). The former solution might
have a footprint of 0.965 by 0.930 inches (0.898 square inches), while the latter leads to acombined footprint of 0.916 by 0.787 inches (0.721 square inches).
Figure 1.

Footprint comparison
0.965 inches
0.916 inches

0.787 inches

0.697 inches

0.930 inches

0.453 inches

SOH28

Competitor’s solution

SRAM
AI02446

October 2011

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Revision history

AN1000

Revision history
Table 1.

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Document revision history

Date

Revision

ChangesNov-2001

1

Initial release.

04-Oct-2011

2

Updated title, products, Figure 1; revised document presentation.

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