L6924U datasheet(24/38 Pages) STMICROELECTRONICS

Part #	L6924U

Description	USB compatible battery charger system with integrated power switch for Li-Ion/Li-Polymer

PDF	38 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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24 / 38 page

Application information: monitoring and protection

L6924U

24/38

8.1

NTC thermistor

The device allows designers to monitor the battery temperature by measuring the voltage

across an NTC or PTC resistor. Li-Ion batteries have a narrow range of operating

temperature, usually from 0 °C to 50 °C. This window is programmable by an external

divider which is comprised of an NTC thermistor connected to GND and a resistor

connected to VREF. When the voltage on the TH pin exceeds the minimum or maximum

voltage threshold (internal window comparator), the device stops the charge process, and

indicates a fault condition through the status pin.

When the voltage (and thus, the temperature), returns to the window range, the device re-

starts the charging process. Moreover, there is a hysteresis for both the upper and lower

thresholds, as shown in Figure 18.

Note:

TBAT = OK when the battery temperature between 0 °C and 50 °C

Figure 17.

Battery temperature control flow chart

Figure 18.

Voltage window with hysteresis on TH

MINTH

MAXTH

MINTH_HYS

MAXTH_HYS

900mV

780mV

225mV

248mV

Voltage

Variationon THpin

Charge disable

Charge enable

L6924U Datasheet(PDF) 24 Page - STMicroelectronics