L6924U datasheet(25/38 Pages) STMICROELECTRONICS

25 / 38 page

L6924U

Application information: monitoring and protection

25/38

When the TH pin voltage rises and exceeds the VMINTH = 50 % of VREF (900 mV typ), the

L6924U stops the charge, and indicates a fault by the status pins. The device re-starts to

charge the battery, only when the voltage at the TH pin goes under VMINTH_HYS = 780 mV

(typ).

For what concerns the high temperature limit, when the TH pin voltage falls under the

VMAXTH = 12.5 % of VREF (225 mV Typ.), the L6924U stops the charge until the TH pin

voltage rises at the VMAXTH_HYS = 248 mV (Typ.).

When the battery is at the low temperature limit, the TH pin voltage is 900 mV. The correct

resistance ratio to set the low temperature limit at 0 °C can be found with the following

formula:

Equation 12

Where RUP is the pull-up resistor, VREF is equal to 1.8 V, and RNTC0°C is the value of the

NTC at 0 °C. Since at the low temperature limit VMINTH = 900 mV:

Equation 13

It follows that:

Equation 14

Similarly, when the battery is at the high temperature limit, the TH pin voltage is 225 mV. The

correct resistance ratio to set the high temperature limit at 50 °C can be found with the

following formula:

Equation 15

Figure 19.

Pin connection

NTC

REF

MINTH

NTC

REF

MAXTH

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