AN1000 Datasheet, PDF (1/3 Pages) STMicroelectronics – Application note

AN1000
Application note
Reduced footprint ZEROPOWER^® and TIMEKEEPER^® supervisor
surface-mount solution
Introduction
The ZEROPOWER^® and TIMEKEEPER^® supervisors from STMicroelectronics (such as the
M40Z300W and the M48T201V/Y) offer all the advantages of using surface-mount
technology, and are well suited to automatic assembly-line processes.
Designed to be highly modular, they interface directly with commodity SRAM, and use a
commercially available cell for the internal battery (which is easily replaceable). These
devices 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 the
two 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 a
combined footprint of 0.916 by 0.787 inches (0.721 square inches).
Figure 1. Footprint comparison
0.965 inches
0.916 inches
0.453 inches
Competitor’s solution
SOH28
SRAM
AI02446
October 2011
Doc ID 5979 Rev 2
1/3
www.st.com