TMP468: Using BJT without collector

Noam Tziony

Intellectual 330 points

Part Number: TMP468

Hi,

I like to use the TMP468 with a 2N3904 die as follows:

Base = D+

Emitter = D-

Collector = No-connection. Will be left floating (die back)

How not using the collector will impact the TMP468 temperature sensing accuracy?

Thanks,

Noam

over 6 years ago

0 David Vaseliou over 6 years ago

TI__Expert 6820 points

Hi Noam,

What is the need to use the above configuration? We recommend using the options on page 30 and 31 in the datasheet.

0 Noam Tziony over 6 years ago in reply to David Vaseliou

Intellectual 330 points

Hi,
As you can see here:
siliconsupplies.com/.../2N3904.pdf

Only the emitter and base are accessible using wire-bonding. The collector is the die back. This is why I don't like to use the collector...

0 David Vaseliou over 6 years ago in reply to Noam Tziony

TI__Expert 6820 points

Hi,

If collector is left open the temperature reading will NOT be accurate.

0 Noam Tziony over 6 years ago in reply to David Vaseliou

Intellectual 330 points

Hi,

Could you please be more specific?

Would I have temperature shift error?

Approximately, what will be the error in C?

Could I calibrate it?

Thanks,

Noam

0 David Vaseliou over 6 years ago in reply to Noam Tziony

TI__Expert 6820 points

Hi Noam,

The error would be based on the η-Factor of the BJT. To calibrate the BJT in the above configuration I would recommend collecting temperature readings across junction temperature and then calculate your η-Factor correction value. After determining this value please set this value in the η-Factor Correction Register to check if it was calibrated correctly. You can use the below app not for reference.
www.ti.com/.../sboa173.pdf

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TMP468: Using BJT without collector