TMP451: Questions about the spec.

Jack Shen2

Part Number: TMP451

We have few questions about the TMP541.

1. Our CPU's diode spec. is 10uA to 230uA and TMP451's remote sensor source current is 120uA. Does that mean TMP451 can be used for the CPU?

2. If so, How to calculate the current which pass through the filtering circuit? You may take the recommendation which are 100pF with 50 ohms values as example.

3. How fast is the internal BJT doing the switching?

4. Is there a length limitation for D+/D-?

5. Can TMP451 support reading the voltage slope of (-1.52mV/C) requirement? If not, may I have your recommendation?

Thank you.

over 2 years ago

0 Nicole Khoury over 2 years ago

TI__Expert 8960 points

Hi Jack,

Thank you for posting to the Sensing forum.

I believe that the customer's listed diode current specification should be fine. Please refer to our Transistor Selection Guide application report for further test results and selection details.

Jack Shen2 said:
3. How fast is the internal BJT doing the switching?

This is something I will have to confirm with our design team.

Jack Shen2 said:
4. Is there a length limitation for D+/D-?

If the length is greater than 8 inches, use a twisted, shielded pair with the shield grounded as close as possible to the TMP451. Please see section 10.1 of the device datasheet for more layout information.

Jack Shen2 said:
5. Can TMP451 support reading the voltage slope of (-1.52mV/C) requirement? If not, may I have your recommendation?

The local and remote temperature sensors have a resolution of 12 bits (0.0625°C).

Best regards,

Nicole

0 Jack Shen2 over 2 years ago in reply to Nicole Khoury

TI__Expert 4015 points

Thanks for the reply, Nicole.

Regarding the resolution, understand that TMP451 has a resolution of 12 bits, but how do I convert it to mV/°C? Could TMP451 meet the following RF demodulator's diode spec.?

0 Nicole Khoury over 2 years ago in reply to Jack Shen2

TI__Expert 8960 points

Hi Jack,

I am not very familiar with the LTC5586, but I believe this implementation should be fine as long as the differential capacitance introduced is not too large.

Please see Figure 6 from the TMP451 datasheet below for how differential capacitance affects the remote temperature error:

Best regards,

Nicole

0 Jack Shen2 over 2 years ago in reply to Nicole Khoury

TI__Expert 4015 points

Thank you Nicole.

Regarding the question about the internal BJT switching frequency, the intend was to know what the sample rate is and how long TMP451 would read the internal temperature and remote temperature.

Thanks.

+1 Nicole Khoury over 2 years ago in reply to Jack Shen2

TI__Expert 8960 points

Hi Jack,

The total time for both remote and local conversions will be a maximum of 34 ms. This can be seen in Section 6.5 – Electrical Characteristics.

Best regards,

Nicole

0 Jack Shen2 over 2 years ago in reply to Nicole Khoury

TI__Expert 4015 points

Thank you for the support, Nicole.

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TMP451: Questions about the spec.