AN3060 datasheet(11/23 Pages) STMICROELECTRONICS

Part #	AN3060

Description	Applications guide for serial real-time clocks

PDF	23 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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11 / 23 page

AN3060

Switchover voltage

Doc ID 16253 Rev 2

11/23

Maximum battery levels

The maximum value for VBAT varies within ST's family of serial RTCs. It is a function of the

process used to fabricate the silicon and considerations made during the design process.

For most parts, the maximum value is VCC(max) (usually 5.5 V).

For parts with VCC as the limit, if VBAT exceeds VCC, parasitic diodes, inherent in CMOS

technology, can be turned on thereby causing problems within the devices. Obviously, it is

okay for VBAT to be above VCC during backup (when VCC is 0). But when operated in active

mode, VBAT should not exceed VCC for these parts.

To be clear, when VCC is the listed limit for VBAT, the limit is the actual working level of VCC

and not VCC-MAX. Conversely, when the limit is VCC(max), the VBAT limit is VCC(max)

regardless of the operating level of VCC.

AN3060 Datasheet(PDF) 11 Page - STMicroelectronics