TIMEKEEPER products

AN1012

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Doc ID 6395 Rev 4

5.2

TIMEKEEPER products have seen a continuous evolutionary cycle since their initial market

introduction in the 1990s.

5.2.1

M48T02 and M48T12

The first TIMEKEEPER products released were the MK48T02 and MK48T12 which offered

2K x 8 RAM and employed the STMicroelectronics 2.0

μm Spectrum™ CMOS technology.

When released, these products included a BR1225 lithium cell with a specified 39 mAh

capacity. This combination offered the user approximately 3.5 years of continuous battery

backup life. Since that time, the devices have been moved to the 4T cell technology

(HCMOS4PZ) and a CAPHAT™ package revision which includes a larger capacity lithium

cell (120 mAh BR1632) capacity, and new part numbers (M48T02/12). These changes

increased the expected battery life to 19 years at 60°C.

Figure 6 shows expected battery lifetime versus temperature with 100% battery backup. The

data shows that by operating the devices at various temperatures, designers can expect a

battery life approaching 20 years under most conditions.

Figure 6.

M48T02/12 data retention lifetime vs. temperature (120 mAh, 100% battery

backup)