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LMX2531: LE signal issue

Jeffrey Chung1
Expert 2480 points
Part Number: LMX2531

Hi,

It says that "LE can be kept high if bit R5[23] is changed to 0 (from its default value of 1). If this bit is changed, then the operation of the part is not ensured because it is not tested under these conditions" in page 19 of datasheet. I want to know what issue is occurred if LE is kept high. Also if LE signal has to be kept low after programming, please let me know how to work the MCU as maximum operation frequency of 20MHz.

Regards,

  • 0
    TI__Mastermind 27581 points

    Jeffry,

    We found during characterization that the there was excessive current going through the LE pin and potentially powering up something that should not have been.

    So if LE is low, no issue. But if LE is high, we have this excessive current and this block drawing current.  Aside from excessive current draw, we are unsure what other undesired impacts there could be.  For instance, we don't know if there is any other issues at hot or cold temperature, as we did not evaluate this in this mode.

    But if you set R5[23] = 1, it sets up a mode that disables this block so then there is no issue.

    For 20 MHz MCU, this works out to 50 ns pulse for LE to be high, so this should not be that big of an issue.

    Regards,

    Dean

  • 0 in reply to Dean Banerjee
    Expert 2480 points

    Hi Dean,

    Thanks for your support. You mean that it is not recommend to 50 ns pulse for LE to be high. Is it correct?

    Also, What is the recommended operation clock range of Microwave? Please let me know that.

    Regards,

  • 0 in reply to Dean Banerjee
    Expert 2480 points

    Hi Dean,

    Could you response on my previous post? Please refer to my previous post.

    Regards,

  • 0 in reply to Jeffrey Chung1
    TI__Guru* 81580 points

    Hi Jeffrey,

    Let me use my language to repeat what did Dean say.

    when LE is pulled HIGH, somewhere in the chip will draw high current. So it is not recommended to pull LE pin HIGH for a long period of time unless R5[23] is set to 1.

    in normal uWIRE programming, with 20MHz clock rate, the HIGH duration of a clock pulse is only 50ns, which is a very short period of time and therefore won't hurt the chip.