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# BQ25886: How to program temperature window

Part Number: BQ25886

The data sheet says

"Temperature Qualification Voltage – Connect a negative temperature coefficient thermistor. Program temperature window with a resistor divider from REGN to TS to GND. Charge suspends when TS pin is out of range. Recommend 103AT-2 thermistor."

I already have a 2-cell battery with a set thermistor and operating temp range. How do I set this range using the divider at S1?

• thermistor is 10k with 3435 B value

• Hi Mike,

For JEITA Guidelines, an appropriate temperature range for a Li-ion or Li-Poly battery is between 0C and 60C. Using this information, appropriate values for RT1 and RT2 can be derived using the given equation:

The values in the equation are:

-Thermistor resistance (RNTC,T1) at 0C and Thermistor resistance (RNTC,T5) at 60C.

-Expected voltage at TS at 0C (VT1) and expected voltage at TS at 60C (VT5)

VT1 and VT5 are expressed as percentages of REGN:

Given typical values VT1 = 34.375% (0.34275) and VT5 = 73.25% (0.7325)

Solving for RT1 and RT2 will provide the appropriate resistor values for your charger to operate effectively within the JEITA guideline temperature range.

Best Regards,

Juan

• Thank you much!

• Happy to help!