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LMP91300: LMP91300 IC Programming

Susmitha K
Prodigy 40 points
Part Number: LMP91300

Hi,

Currently I am working with LMP91300 IC for proximity sensor application in NPN configuration and I am facing some issues. There is a problem while testing with the default values. Based on datasheet, there are default values in the registers. So first, I tried to test with the default condition and check the distance at which metallic objects can be sensed. According to datasheet, there is no difference in the waveform while it senses and when its far away from the metallic object.

Subsequent questions:

  1. Will the LED blink while it senses the metallic object or what is its function?
  2. My target distance is 30mm. Is it possible to achieve this distance by adjusting the LC values and Rp value limit mentioned in the datasheet.
  3. The programming Board LMP91300_SWIF_EVM is not available online. Let me know the viable alternative to change the default parameters of LMP91300.

I have attached the Schematic diagram of the board I am working with.

Thanks in advance.

  • 0
    TI__Mastermind 18545 points

    Hello, 

    The LED function can be programmed using the OUT_CONFIG_INIT register of the device. Depending on the settings there, the LED may either switch on or switch off when metal is present. You will also have to set the detection threshold for the LED to switch states. 

    For detection distance, the Rp limits set when the proximity data of the device will be at min and max values: 

    What are you currently using for the LC tank and do you get any switching output by bringing the metal very close the LC tank? Is 30mm a fixed distance requirement for the system? 

    For the LMP91300_SWIF_EVM, there have been some work arounds done in the past (see this E2E thread) but it isn't something we have an active alternative for. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 40 points

    Hi,

    As of now, I am testing with the default values in the IC. 30mm is my target distance.

    1. Is it possible to find the default Rp value by testing with the values pre-set in the registers.

    2. How can I find the Rp value of the LC tank ? Can you explain this with an example?

    3. I need help with programming the LMP91300 board. Is the firmware code for programming the LMP91300_SWIF_EVM is available? or where can I get the evaluation board?

  • 0 in reply to Susmitha K
    TI__Mastermind 18545 points

    Hello, 

    You can determine the Rp of the LC tank by following one of the methods mentioned in this document: Measuring Rp of an L-C Sensor for Inductive Sensing

    We don't sell the evaluation board anymore and don't maintain the firmware code. Your best bet for replicating this would be the previously linked E2E post. 

    I have a few more questions for you on the application implementation:

    • Is this a new design or existing design you are working with?
    • What is the motivation for using the LMP91300 instead of one of our LDC devices? 
    • What does your target motion look like? 
    • What material is your target made out of and how large is it?

    Thank you, 
    Justin