BQ24081: thermal resistance RT1 and RT2 design

Tommy Tzeng

Part Number: BQ24081

Hi Sir,

how to design RT1 and RT2 value?any have tools for calculation?

i use a thermistor 103AT type, i need to range from 5 degrees to 45 degrees, so i need to add an external resistance design.can help us?

over 7 years ago

0 Bill Johns over 7 years ago

TI__Guru* 76756 points

Hello
Can you change the NTC ?
With the 103AT it is difficult to hit 5C and 45C, it will work well for 0C and 45C.

0 Tommy Tzeng over 7 years ago in reply to Bill Johns

Genius 5970 points

Hi Sir,

may i know why? it is possible to use an external resistance to change the protection threshold for high and low temperaatures.

0 Bill Johns over 7 years ago in reply to Tommy Tzeng

TI__Guru* 76756 points

The external resistance can be used to increase the temp range. In this application we want to decrease the temp range. NTC will need to change resistance value quicker with themp change, the Beta needs to increase.
I am estimating that for a 10k the Beta would need to increase to 3800k or greater, 103AT Beta is 3435.

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BQ24081: thermal resistance RT1 and RT2 design