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LMK62I0-100M: LMK62I0-100M OE pin 1

Björn Hellerstedt
Prodigy 180 points
Part Number: LMK62I0-100M
Other Parts Discussed in Thread: LMK61E2EVM

This question regards the OE pin on this device.

In page 3 of DS pin 1 is described:

"Outputenable(internalpullup).Whensettolow,outputpairisdisabledandsetathigh impedance."

Is this true that this pin have an internal pullup?

When I measure the voltage on this pin it is low and I have to pull it high to get the 100Mhz output....

Thank you for your help!

  • 0
    TI__Expert 7030 points

    Hi Bjorn, 

    Can you provide the schematic or setup you are using to probe the OE pin voltage? Unfortunately we don't have any LMK62 units in the office, but I just checked on a LMK61E2EVM (which should have the same OE behavior) and I saw the OE pin was pulled up internally and the output was enabled even when the OE pin was left floating. 

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    Prodigy 180 points

    Hello

    Thank you for your reply. Did you measure 3.3v at pin 1 ( OE) ?

    This is my schematic.

    I measure 0 v at pin 1 on U208. The pin (was) floating.

    I connected pin 1 via pin 6 and it works.

    Please let me know what you think.

  • 0 in reply to Björn Hellerstedt
    TI__Expert 7030 points

    Hi Bjorn, 

    I measured 1.8V on the OE pin when it was left floating. Just to confirm, TP211 is completely isolated and there's no way that it could accidentally be pulling down the OE pin? It may be helpful if you could also include some images of the board layout if possible. Also, can you provide the top marking of the LMK62 device you are using?

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    Prodigy 180 points

    Hello

    Measured pin 3 on 3 different boards in this batch, TP211 measures x mV.

    If I measure resistance between TP211 and GND I have about 30.3k ohm.

    See attached picture from PCB. Only top layer is involved.

    If I read the text on the device:

    TI 6210

    1BZEV53

    10000

    Thank you so much for your help.

  • 0 in reply to Björn Hellerstedt
    TI__Expert 7030 points

    Hi, 

    Your schematic and layout look good to me, so the OE behavior you're seeing is definitely strange. I found an LMK62 board in the office, I will test it out on Monday and confirm the OE functionality.  

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    Prodigy 180 points

    Hello

    I have order 7 more pcs of LMK6210-100M from the same sample order ( EMS-stock ), they are not mounted on a PCB.

    This means I will add 3.3v and measure on pin 1 and report back to you. In case of they are fulty ( or documentation is wrong) I would like you to create an RMA ASAP since it looks like this is  a serious problem from your side. I can send you the pcs.

    Please let me know what you think.

    Thanks

    Björn Hellerstedt

  • 0 in reply to Connor Lewis
    Prodigy 180 points

    Hello Connor

    Have you done any test? 

    BR

    Björn H

  • 0 in reply to Björn Hellerstedt
    TI__Expert 7030 points

    Hi Björn, 

    I did a quick check on our LMK62 EVM and I'm seeing the same type of behavior that you're describing (no output unless the OE pin is pulled high). I'm talking with the design team now to see if this is a typo on the datasheet, I'll let you know if there are any updates. 

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    TI__Expert 7030 points

    Hi Björn,

    I had a discussion with our design team and we confirmed that this is a datasheet typo, and this device does not have an internal pullup on the OE pin. We will be making an update to the datasheet to specify that an external pullup is required. Thanks for bringing this to our attention, and let me know if you have any other questions. 

    Regards, 

    Connor