LM95071: Temperature Accuracy

Sadanori Kato

Part Number: LM95071
Other Parts Discussed in Thread: LM71, LM71-Q1

Hi,

The expected accuracy cannot be obtained due to the temperature transition when using the power supply at 3.3 V, so could you please tell me the root cause ?

Best regards,
Kato

over 7 years ago

0 Brandon Fisher94 over 7 years ago

TI__Mastermind 28075 points

Hello Kato-san,

What type of heat source are you monitoring? If you are attempting to monitor ambient temperature and it differs significantly from your board temperature that could slow the temperature response time of the device.

Best Regards,
Brandon Fisher

0 Sadanori Kato over 7 years ago in reply to Brandon Fisher94

Guru 36540 points

Hi Brandon-san,

Thank you for your response.

The board temperature is measured by using multiple LM95071.
Our customer has confirmed the same symptom as the following post and LM95071 will operate normally by restarting the device(power-on/off) if a temperature different from the expected value is detected.
Could you please tell me the root cause ?

Spurious negative temperature readings with LM95071
https://e2e.ti.com/support/sensor/temperature_sensors/f/243/t/454653

Best regards,
Kato

0 Brandon Fisher94 over 7 years ago in reply to Sadanori Kato

TI__Mastermind 28075 points

Hello Kato-San,

I am currently looking into this for you and I will get back to you within 1-2 days.

Best Regards,
Brandon Fisher

0 Sadanori Kato over 7 years ago in reply to Brandon Fisher94

Guru 36540 points

Hi Brandon-san,

Thank you for your support.

I am looking forward to getting the information soon.

Best regards,
Kato

0 Sadanori Kato over 7 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Brandon-san,

Sorry for rushing you, but please let me know the current status on this issue.
I should report the following items to our customer, so could you please give me your advice soon ?

<Customer Request>
- Presence or absence of the same symptom in the past
- Root cause
- Workaround

Best regards,
Kato

0 Brandon Fisher94 over 7 years ago in reply to Sadanori Kato

TI__Mastermind 28075 points

Hello Kato-san,

Your customer's experience with LM95071 are part of a known issue with the device. Polling the LM71 and LM95071 much faster than the conversion time can cause erroneous readings. As a workaround we recommend polling the device more slowly. We will be releasing an errata related to this in the coming weeks.

Best Regards,
Brandon Fisher

0 Sadanori Kato over 7 years ago in reply to Brandon Fisher94

Guru 36540 points

Hi Brandon-san,

Thank you for the information.

Our customer's product is nearing mass production, so our customer has no time to lose.
I have already sent a friend request to you, then could you please share the content which will be described in an errata(root cause & workaround) via a private message on e2e with me in advance ?

Best regards,
Kato

0 Sadanori Kato over 7 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Brandon-san,

Could you please tell me the recommended SC clock period(10us / 100us / 1ms / etc) to obtain the expected accuracy ?

Best regards,
Kato

0 Ren Schackmann over 7 years ago in reply to Sadanori Kato

TI__Mastermind 44245 points

Hi Kato-san,

We recommend to read temperature only once per conversion time which is 228ms max. The frequency or clock period is not related to the issue.

Thanks,
Ren

0 Sadanori Kato over 7 years ago in reply to Ren Schackmann

Guru 36540 points

Hi Ren-san,

Thank you for the information.

I understood and will inform that workaround to our customer.
By the way, could you please tell me when an errata would be released ?

Best regards,
Kato

0 Sadanori Kato over 7 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Ren-san,

I have already informed the workaround to our customer, but he is so frustrated.
So, I have already sent a friend request to you, then could you please provide the root cause which will be mentioned in an errata via a private message on e2e in advance ?
In addition, it is pointed out that the mention for the following /CS signal is erroneous. However, I think that the above conditions can also be applied if the serial clock frequency is very slow.
* I changed the content of the description a bit.

Best regards,
Kato

0 Sadanori Kato over 7 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Ren-san,

I have one more request, so could you please revise LM95071 data sheet ?

Best regards,
Kato

0 Ren Schackmann over 7 years ago in reply to Sadanori Kato

TI__Mastermind 44245 points

Hi Kato-san,

I agree that the datasheet is wrong and needs to be corrected. At this time, I can't provide a timeline for this activity. Additionally, I can't share further information about a possible errata outside TI. Please contact us directly through your TI Sales Representative.

Thanks,
Ren

0 Ren Schackmann over 7 years ago in reply to Sadanori Kato

TI__Mastermind 44245 points

Hi Kato-san,

Please reference the errata released for LM71. This errata also applies to LM95071. We are working to have the errata linked to LM95071 as well.

www.ti.com/.../snla296.pdf

Thanks,
Ren

0 Sadanori Kato over 7 years ago in reply to Ren Schackmann

Guru 36540 points

Hi Ren-san,

Thank you for your strong support.

I will refer to "LM71/LM71-Q1 Errata" and inform this information to our customer instead of LM95071 errata.
In addition, I will discuss this issue with TI local member.

I greatly appreciate your cooperation.

Best regards,
Kato

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LM95071: Temperature Accuracy