M48T58 datasheet(18/31 Pages) STMICROELECTRONICS

18 / 31 page

Clock operations

M48T58, M48T58Y

18/31

Figure 8.

Crystal accuracy across temperature

Figure 9.

Clock calibration

6.5

Battery low flag

The M48T58/Y automatically performs periodic battery voltage monitoring upon power-up.

The Battery Low flag (BL), Bit D6 of the flags Register 1FFDh, will be asserted high if the

internal or SNAPHAT® battery is found to be less than approximately 2.5V and the Battery

Low Enable (BLE) Bit has been previously set to '1.' The BL flag will remain active until

completion of battery replacement and subsequent battery low monitoring tests.

If a battery low is generated during a power-up sequence, this indicates that the battery

voltage is below 2.5V (approximately), which may be insufficient to maintain data integrity.

Data should be considered suspect and verified as correct. A fresh battery should be

installed.

The SNAPHAT top may be replaced while VCC is applied to the device.

AI02124

-80

-60

-100

-40

-20

ΔF

= -0.038

(T - T

2 ± 10%

ppm

0 = 25 °C

ppm

°C

AI00594B

NORMAL

POSITIVE

CALIBRATION

NEGATIVE

CALIBRATION

M48T58 Datasheet(PDF) 18 Page - STMicroelectronics