LM95071: Temperature readings stop working (continued)

Lauren Mayfield

Part Number: LM95071

Hello,

I am asking this question as a follow up from this previous post:

e2e.ti.com/.../lm95071-temperature-readings-stops-being-accurate-after-a-few-days-of-working-properly

They figured out the issue. There are several interrupts that are asynchronous to the temperature measurement, over the course of a few days on of them eventually interrupts the function that reads the temperature, and the interruption (extension of the sclk or /cs) is putting the LM95071 into shutdown mode, where after it only will output the device ID. To correct the issue they have moved the read function to inside one of the interrupts so it cant be interrupted itself.

Now the question is how can an interruption of a 2 byte read result in the device in shutdown mode. According to the data sheet you must write FFFF after the 2 byte read to accomplish this?

Thanks,

Lauren

over 4 years ago

0 Brandon Fisher94 over 4 years ago

TI__Mastermind 28070 points

Hi Lauren,

Thank you for coming back and sharing their solution.

Its difficult to say for certain what could cause this without seeing the transaction that was placing the device in shutdown, but your assessment is correct, they would have had to write 0xFF to place the part into shutdown mode, or this transaction would have to have been replicated in some way.

In practice, this could occur if the CS was not released, and another 16 clock cycles were issued by the controller. The LM95071 would not drive the SI/O line in this case, and because they do not have the line connected to MOSI it would just have to be above 0.7VDD during the 16 clock cycles to trigger shutdown mode.

Best Regards,
Brandon Fisher

Sensors

Sensors forum

LM95071: Temperature readings stop working (continued)