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STC3115

Functional description

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6.4

Power-up and battery swap detection

When the STC3115 is powered up at first battery insertion, an automatic battery voltage

measurement cycle is made immediately after startup and debounce delay.

This feature enables the system controller to get the SOC of a newly inserted battery based

on the OCV measured just before the system actually starts.

Figure 8. Timing diagram at power-up

A battery swap is detected when the battery voltage drops below the undervoltage lockout

(UVLO) for more than 1 s. The STC3115 restarts when the voltage goes back above UVLO,

in the same way as for a power-up sequence.

Such filtering provides robust battery swap detection and prevents restarting in case of short

voltage drops. This feature protects the application against high surge currents at low

temperatures.

Figure 9. Restart in case of battery swap

Example: When BATD/CD is high (voltage above the 1.61 V threshold) for more than 1 s, a

battery swap is detected. The STC3115 restarts when the BATD/CD level returns below the

threshold, in the same way as for a power-up sequence.

Using the 1-s filter prevents false battery swap detection if short contact bouncing occurs at

the battery terminals due to mechanical vibrations or shocks.

VCC

UVLO

Short UVLO

event < 1s

No restart,

No operation

interuption

<1s

Long battery disconnection

events > 1s

STC3115 restarts

>1s

POR