STBC02 datasheet(32/39 Pages) STMICROELECTRONICS

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Operation description

STBC02

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DocID029261 Rev 2

8.3

Battery temperature monitoring

The STBC02 integrates all the needed blocks to monitor the battery temperature through

an external NTC resistor. The battery temperature monitoring is enabled only during the

battery charging process, in order to save power when the system is supplied from the

battery.

When the battery temperature is outside the normal operating range (0-45 °C), the

charging process is halted, an alarm signal is activated (the CHG pin toggles at 16.2 Hz)

but the charging timeout timers are not stopped.

If the temperature goes back to the normal operating range, before the maximum charging

time has elapsed, the charging process is resumed and the alarm signal is cleared.

In case of the charging timeout expires and the temperature is still outside the normal

operating range, the charging process is stopped but it can be still restarted using the CEN

pin.

Both temperature thresholds feature a 3 °C hysteresis. The battery temperature monitoring

block is designed to work with an NTC thermistor having R25

= 10 kΩ and ß = 3370

(Mitsubishi TH05-

3H103F). If an NTC thermistor is not used, 10 kΩ resistor must be

connected to ensure the proper IC operation.

8.4

Battery overcharge protection

The battery overcharge protection is a safety feature, active when a valid input voltage is

connected, preventing the battery voltage from exceeding a VOCHG value. Should an

overcharge condition be detected, the current path from the input to the battery is opened

and a fault signal is activated (the CHG pin toggles at 8.2 Hz). When the battery voltage

goes below VOCHG, normal operations can only be restarted by disconnecting and

connecting back again the input voltage (VIN).

8.5

Battery over-discharge protection

The battery over-discharge protection is a safety feature enabled only when no valid input

voltage source (VUVLO < VIN < VINOVP) is detected. Therefore, when the STBC02 and the

system are powered off from the battery, an over-discharge of the battery itself is avoided.

Should the battery voltage level be below VODC for more than tODD (over-discharge state),

the STBC02 turns off and current sunk from the battery is reduced to less than 50 nA.

When a valid input voltage source is detected, while the battery is in an over-discharge

state, the STBC02 charger, SYS and LDO outputs are enabled. This condition persists until

the battery voltage has exceeded the over-discharge released threshold (VODCR), otherwise

any other disconnection of a valid input voltage source brings back the STBC02 to a

battery over-discharge state.

8.6

Battery discharge overcurrent protection

When the STBC02 is powered off from the battery connected to the BAT pin, a discharge

overcurrent protection circuit disables the STBC02 if the current sunk from the battery is in

excess of IBATOCP (whose value is programmable via SWIRE) for more than tDOD.

The presence of a valid input voltage source or triggering the WAKE-UP input pin, allows

normal operating conditions to be restored.

8.7

Battery fault protection

The STBC02 features a battery fault protection. The STBC02 charger is stopped if the

battery voltage remains below 1 V for at least 16 seconds.

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