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TEMP. SENSOR LM95071

eli
Guru 13485 points
Other Parts Discussed in Thread: LM95071

See below questions:

I'm using LM95071 Temperature Sensor in my system. Sometimes I get faulty temperature information: T= - 255.906 oC.

It looks like the LM95071 enters shutdown mode and the data on the SPI is the MANUFACTURER ID.

In my application I'm not using shutdown mode in any case.

1. How the LM95071 can enters shutdown mode (except writing XX FF hex to the LM95071 by the SPI Master)?

2. Is it any known errata for the LM95071?

  • 0
    TI__Expert 4905 points

    Hi Eli,

    Sorry haven't heard of this issue before, but I'm checking to make sure. If you have a noisy clock then that would be an issue. perhaps you can try a small cap on the clock pin to help filter noise out. Is the next read after the -255.906 a valid temperature? If it is then it's not getting in the shutdown mode as you would have to program it to change modes.

     

    Take care,

  • 0 in reply to Emmy Denton
    Guru 13485 points

    Hi,

    The next read is invalid temperature as well (same value -255.906). BTW, the MANUFACTURER ID data in temperature representation giving -255.906…

    The Clock, CS and Data signals looks good…

     

  • 0 in reply to eli
    Prodigy 10 points

    I got this when driving the device from an FPGA.

    Even though I only ever read from the device, I still had to drive a low into it before my read cycle. An FPGA-input pin effectively lets the SIO line float high, which clocks 1's into the device putting it in shutdown-mode. I used a read cycle with say, 24 clocks per read, where the first 8, I drove the SIO line low.

    Alternatively use a pull down resistor on SIO. Apologies if I forget the exact terminoloy used on the datasheet.

  • 0 in reply to John Honor
    TI__Expert 4905 points

    Hi John,

    So it seems you have solved your problem. This is not a known problem with the part it is known behavior and it seems like you have found some great work arounds.

    Take care,