Powerup sequence Reset mode

RESET mode can be entered in four ways: by inserting the battery or charger, by RTC alarm or by pressing the power key. After voltage appearing at UEM's pin UEMRSTX (connected to AEM's pin REFENA) is used as indication for AEM to start up HW regulators. Also VCTXO is Powered up by using VR3 (UEM). After the 220 ms delays regulator are configured and UEM enters PWR_ON mode and system reset PURX is released.

During system start-up, in RESET state, the regulators are enabled, and each regulator charges the capacitor(s) at the output with the maximum current (short circuit current) it can deliver. This results in battery voltage dropping during the start-up. When a battery with voltage level just above the hardware cutoff limit is inserted, the system may not start due to excessive voltage dipping. Dropping below 2.8 V for longer than 5 us forces the system to PWR_OFF state.

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DIY Battery Repair

DIY Battery Repair

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