AN1012 datasheet(16/33 Pages) STMICROELECTRONICS

16 / 33 page

TIMEKEEPER products

AN1012

16/33

Doc ID 6395 Rev 4

5.2.3

M48T58

The next TIMEKEEPER® product was the M48T58 which is fabricated on the 0.6 µm,

double-level metal HCMOS4PZ process for 4T SRAM cells.

Table 13 on page 28, Appendix C: TIMEKEEPER® products on page 28, Figure 8, and

Figure 9 on page 16 show the extent to which the data retention of these devices is more

dependent on temperature. Higher temperatures cause lower resistor values (and therefore,

higher currents) because of the negative temperature coefficient of the poly-R resistors.

Data retention lifetimes typically range from 8.6 years (at 30 °C) for devices in the

CAPHAT™ package, with a 48 mAh battery (see Figure 8), and up to 20 years (and more)

for the SNAPHAT package with a 120 mAh BR1632 battery (see Figure 9). As always,

several factors affect battery lifetime, including the VCC duty cycle and temperature.

Figure 8.

M48T58 data retention lifetime vs. temperature (48 mAh, 100% battery

backup)

Figure 9.

M48T58 data retention lifetime vs. temperature (120 mAh, 100% battery

backup)

AN1012 Datasheet(PDF) 16 Page - STMicroelectronics