TMP451: remote temperature error vs series resistance

Hiroshi Sato

Part Number: TMP451

Hello,

Our customer have a question for datasheet figure 5, so please give us your advice.

"Series Resistance" means the case when the resistances connected to D+ and connected to D- are the same value, right ?

And if so, could you provide any data when the resistances are different D+ and D- (for example, D+=1k ohm with D-=0.8k and 1.2k ohm)?

Thanks and best regards,

Hiro

over 6 years ago

0 Jose Arteaga4 over 6 years ago

TI__Expert 5695 points

TI support team will contact you shortly.

0 William Santos56 over 6 years ago

TI__Prodigy 390 points

Hiroshi,

The series resistance simply refers to the resistance developed by the length of wire/trace connected to the D+/D- pins. A resistor can be placed there to act as a current limit but if you desire filtering you will need to add a capacitor as well to form a lowpass filter. Figure 5 gives you the remote temperature error as a function of the series resistance: so depending on your wire length/resistance characteristics, you can estimate the error in measurement. As shown in the graph, error of +0.5 degrees Celsius is ensured for series resistances up to 3k ohms.

Regards,
Will

0 Hiroshi Sato over 6 years ago in reply to William Santos56

Expert 2590 points

Hello Will-san,

Thank you for your replying.

Excuse me, I have a question.
Does the recommended series resistance (up to 1k ohm) mean
the total value for wire/trace resistance plus connected D+ resistor plus connected D- resistor ?

Thanks and best regards,
Hiro

0 William Santos56 over 6 years ago in reply to Hiroshi Sato

TI__Prodigy 390 points

Hiroshi-san,

Yes, the recommended resistance is the total value of the series resistance between the D+ and D- pins. The ADC inside the chip interface only sees one node between the D+/D- pins. Thanks

Regards,

Will

0 Hiroshi Sato over 6 years ago in reply to William Santos56

Expert 2590 points

Hello Will-san,

Thank you for your comment and I understand.
I'll explain it to our customer.

Thanks and best regards,
Hiro

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TMP451: remote temperature error vs series resistance