L6924U datasheet(26/38 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]

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26 / 38 page

Application information: monitoring and protection

L6924U

26/38

Where RNTC50°C is the value of the NTC at 50 °C. Considering VMAXTH = 225 mV it follows

that:

Equation 16

Consequently:

Equation 17

Based on equations 14 and 17, it derives that:

Equation 18

The temperature hysteresis can be estimated by the formula:

Equation 19

Where VTH is the pin voltage threshold on the rising edge, VTH_HYS is the pin voltage

threshold on the falling edge, and NTCT (- %/°C) is the negative temperature coefficient of

the NTC at temperature (T) expressed in % resistance change per °C. For NTCT values, see

the characteristics of the NTC manufacturers (e.g. the 2322615 series by VISHAY). At the

low temperature, the hysteresis is approximately:

Equation 20

Obviously at the high temperature hysteresis is:

Equation 21

NTC

225

NTC

HYS

NTC

−

NTC

HYS

−

900

780

900

NTC

HYS

−

225

248

225

L6924U Datasheet(PDF) 26 Page - STMicroelectronics