LM5066I: How is the negative temperature represented

krishna saka

Part Number: LM5066I

HI,

My Question is very specific to READ_TEMPERATURE_1 (8Dh) register . Based on the valued of m ,b and R for this register. It simply reduces to the Y/16 . Where Y = A 2-byte two's complement integer received from device.

But on page 28 . It says the range of this register is 0000h-0FFFh to indicate -256C to 255C . If the range of Y = 0000 to 0FFFh that means the MSB is never set then how are the negative temperature values represented ??

So the details in the data sheet corresponding to this register are not so clear, more info on this would be highly appreciated

over 5 years ago

0 Rakesh over 5 years ago

TI__Guru* 95541 points

Hi Krishna,

Thanks for reaching out!
I will look into this and respond soon.

Best regards,
Rakesh

0 Rakesh over 5 years ago in reply to Rakesh

TI__Guru* 95541 points

Hi Krishna,

I need to try out on hardware to understand. Did you tried at lower temperatures <0C? Can you please share the information.

Best regards,
Rakesh

0 krishna saka over 5 years ago in reply to Rakesh

Prodigy 60 points

Hi Rakesh,

No I was not able to read below 0 Celsius . If i was able to then i would not have asked this question . I do not have means to reduce the temperature below C for the tesnosr.

Is there any way to set a negative offset ? so the current temperature shows below 0 ?

0 Rakesh over 5 years ago in reply to krishna saka

TI__Guru* 95541 points

Hi Krishna,

Got it. I will check.
As I have similar activities in the queue, I will get back to you in the next week after test and verification on hardware.

Best regards,
Rakesh

0 Rakesh over 5 years ago in reply to Rakesh

TI__Guru* 95541 points

Hi Krishna,

Sorry for the delay. I will check the possibility and update you tomorrow.

Best regards,
Rakesh

0 krishna saka over 5 years ago in reply to Rakesh

Prodigy 60 points

Hi Rakesh,

Can you please provide an update ?

We have few implementations pending because of this

0 Rakesh over 5 years ago in reply to krishna saka

TI__Guru* 95541 points

Hi Krishna,

The range for Y should be from F000h to 0FFFh. We are able to measure negative temperature values with out setting negative offset.
Let me know if you face any issue.

Best regards,
Rakesh

0 krishna saka over 5 years ago in reply to Rakesh

Prodigy 60 points

THIS DID NOT RESOLVE MY ISSUE

The range of Y = 0000 to 0FFF
After simplification for the temperature calculation which will result in (Y in decimal )/ 16

So the temperature range will now as below

for Low 0000 = 0/16 = 0 Celsius
for High 0FFF= 4096/16 = 255 Celsius

Now as you can see I cannot see the negative temperature .

Please let me know if I'm doing anything wrong it the calculation .

Please share your data of Y for negative temperature and the calculations you have performed

0 Rakesh over 5 years ago in reply to krishna saka

TI__Guru* 95541 points

Hi Krishna,

I used equation (4) in the datasheet.

The range for Y should be from F000h to 0FFFh.
For Low F000 --> -4096/16 = –256°C
For High 0FFF --> 4095/16 = 255°C

Best regards,
Rakesh

0 krishna saka over 5 years ago in reply to Rakesh

Prodigy 60 points

Hi Rakesh,

Thanks for your reply . Can you please correct the data sheet which tells the range for Y for temperature is from 0000h to 0FFFh , which is wrong

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LM5066I: How is the negative temperature represented