INA330: What to do if thermistor value is lower than 2kΩ?

Timothy Ambrose

Part Number: INA330

Page 7 has the following text:

Values less than 2kΩ can cause the voltage excitation buffers to become unstable

I'm stuck using the ERTJ0EM103J as it is mounted in a buy part. I need to resolve temperatures as high as 120C but the resistance is listed as approximately 400Ω at that temperature. Is there something I can do? I could add a low temp coeff series 2kΩ resistor to Rtherm and populate Rset as 12kΩ to maintain stability but I'm not sure if there are other effects that I'm not anticipating.

over 6 years ago

0 Timothy Ambrose over 6 years ago

Prodigy 140 points

I see that I have to keep I1 and I2 below 125uA so I'll have to adjust Vexcite down to 0.3V.

0 Zak Kaye over 6 years ago in reply to Timothy Ambrose

TI__Mastermind 23050 points

Hi Timothy,

You definitely will have to adjust the excitation voltage as you have mentioned to keep the currents below 125uA. If you do this then I believe you will see the desired operation. I am not certain where the requirement to keep the impedance above 2kOhms comes from, but I believe this is more to keep the currents within the desired range. If you test this and run into issues please let us know and we explore alternative solutions.

0 Timothy Ambrose over 6 years ago in reply to Zak Kaye

Prodigy 140 points

Thanks Zak - I'll try it and report back

- Tim

0 Dennis Goeke over 6 years ago in reply to Timothy Ambrose

TI__Genius 11135 points

Timothy

We haven't heard back from you so we assume this answered your questions. If you need more help just post another reply below.

Thanks
Dennis

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INA330: What to do if thermistor value is lower than 2kΩ?