BQ25302: RT1 and RT2 thermal sensing resistor calculations

Zahidur Rahman

Prodigy 10 points

Part Number: BQ25302

Tool/software:

Good day,

I am struggling to figure out the RT1 and RT2 values based on the datasheet. the formula states:

I am trying to use an NTC thermistor 10k with beta 3435

Which makes RNTCT1 = 29.16K (@0°C) and RNTCT3 = 4.74K (@45°C)

VT1% is 73.5 and VT3% is 47.25.

I have used wolfram alpha, CGPT, a good old fashioned pen/paper/calculator and another engineer, I ALWAYS get a negative value for RT2, I think the formula or the example might be faulty, can someone please advise?

22 days ago

+1 Ning T 21 days ago

TI__Mastermind 48811 points

Hi,

For RT1 and RT2 calculation tool, please refer to http://www.ti.com/lit/zip/slurax7 for the BQ2589x calculator tool. Although it was developed for the BQ2589x, the principle is similar and can be used for BQ2530x with minor changes. If RT1 or RT2 is a negative value, then the thermistor does not work and please try another thermistor. The d/s uses 103AT NTC thermistor as an example.

The calculator is for reference only. Please verify the actual protection temperature range and temperature profile behaviors on boards.

Thanks,

Ning.

0 Zahidur Rahman 21 days ago in reply to Ning T

Prodigy 10 points

The calculator works, but the link is https://www.ti.com/lit/mo/slurax7a/slurax7a.zip?ts=1719389084173

Thank you for your help.

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BQ25302: RT1 and RT2 thermal sensing resistor calculations