• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 48 subscribers
  • Views 959 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

LMP91000: LMP91000 and LMP91002 questions

LMP91000: device measures CO even in the Deep Sleep mode

Bart
Expert 6470 points
Part Number: LMP91000


Team,

our customer has some problem with LM91000:

When I write 000 to [2:0] bits in Mode Control Register (address 0x12), the LM91000 starts measurement and I get expected results for CO even though it is set to Deep Sleep Mode. This is also default mode after power on. In this mode only the I2C communication should work, without measurement. And when I want to put chip in 3-lead amperometric cell ( 011 to [2:0] bits ), or 2-lead ground referred galvanic cell ( 001 to [2:0] bits ), it's not working and I always get the same CO results, without changing. The temperature measurement mode and standby mode work great.

Can you advise what might be the issue?

Thank you

  • 0
    TI__Expert 4875 points
    Hello,

    Could you please check the following items and questions so I can further investigate this problem?

    - Make sure that proper Write and Read Operations are being followed, as specified in section 7.5 of the LMP91000 datasheet.

    - What are the complete values you write to MODECN for Deep Sleep Mode, 3-lead or 2-lead mode, temperature and standby mode?

    - What type of sensor is the customer using; is it 3-lead or 2-lead? They would want to set the register according to the sensor they are using. Also, when they say the sensor is not working, do they mean that the CO value is a wrong value as compared to the expected result?

    Regards,

    Audrey
  • 0 in reply to Audrey Dearien7
    Prodigy 15 points
    Hello,

    I'm sure that I used proper Write and Read Operations, I checked the LM91000 datasheet again.
    I tried to write the next values to MODECN register: 0x00 (or 0x80 when I want to put FET in enabled state) for Deep Sleep Mode, 0x01 (or 0x81) for 2-lead mode, 0x02 (or 0x82) for Standby Mode, 0x03 (or 0x83) for 3-lead mode, 0x06 (or 0x86) and 0x07 (or 0x87) for temperature mode, and always is the same problem.
    I am using the SPEC sensor, type 110-109 in 3-lead mode, and I am trying to run LM91000 in this mode but nothing, the value that I am reading is always the same and unexpected, and without changing. But when I put LM91000 in Stanby Mode, the CO values are good and expected. This is a same situation for Deep Sleep Mode, and that is a strange.

    I hope that you will find where exactly is a problem.

    Best regards,

    Nemanja
  • 0 in reply to Nemanja Medakovic
    TI__Expert 4875 points
    Hi Nemanja,

    Thanks for the information. Firstly, you should not enable FET_SHORT in any mode other than Deep Sleep. This is used to reduce power during Deep Sleep Mode. Secondly, when you enable the Temperature Measurement (TIA OFF) which is 110, you will not get a proper output from the gas sensor because this is only a temperature measurement. For Temperature Measurement (TIA ON), you have to measure the output of the Gas Sensor from pin C2 of the LMP91000, instead of the VOUT pin (because temperature output is now here).

    Which configuration are you most interested in? Is it the Standby, Deep Sleep, and 3-Lead mode? If so, I would recommend you test those modes using the following register configurations.

    Deep Sleep: 0x00 or 0x80
    Standby: 0x02
    3-Lead: 0x03

    Could you also please provide your schematic and waveforms of the output you are seeing (and where you are measuring them).

    Thank you,
    Audrey