L6924D datasheet(26/38 Pages) STMICROELECTRONICS

26 / 38 page

Application information: monitoring and protection

L6924D

26/38

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

L6924D 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 = 780mV (typ).

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

12.5% of VREF (225mV Typ.), the L6924D stops the charge until the TH pin voltage rises at the

VMAXTH_HYS = 248mV (Typ.).

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

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

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

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

It follows that:

Figure 20. Voltage window with hysteresis On TH

Figure 21.

Pin connection

VMINTH

VMAXTH

VMINTH_HYS

VMAXTH_HYS

900mV

780mV

225mV

248mV

Voltage

VariationonTHpin

Charge disable

Charge enable

L6924D

REF

NTC

REF

MINTH

Eq: 9-1

NTC

Eq: 9-2

NTC

Eq: 9-3

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