We are designing a system that has a fairly hefty backbup battery, 500 mAH Li-ion. This system has its own power management circuitry, and we plan to control the power to the module which contains an OMAP3530 and a TPS65930 with our own power mosfet. When main power is removed, we plan to keep the OMAP module powered and running for about 30 seconds so that software can be involved in an orderly shutdown of the system. The 500 mAH Li-ion will power the OMAP during this time, as well as some other circuitry involved in systems that need to be shut down properly. After 30 seconds, we plan to remove power from the TPS65930 via our own system power management circuitry. We do not wish to include a seperate coincell backup in our system to power the BKBAT pin on the TPS65930. So to keep the RTC running in the TPS65930, we plan to connect BKBAT to the 500 mAH Li-ion battery. The 500 mAH Li-ion battery will be charged at a voltage as high as 4.2 volts when the system main power is available, and will have a nominal voltage of 3.6 volts when it is not being charged. The TPS65930/20 data manual (April 2011, swcz001g.pdf) shows on page 24 in Table 3-3 a recommended maximum voltage of 3.3V for BKBAT. No BKBAT constraint is mentioned on the previous page in the Absolute Maximum Ratings. Our question is:
Is it OK to apply voltage that high (4.2 volts) to the BKBAT pin on the TPS65930?
Thanks,
Alberto Pierotti
