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Other Parts Discussed in Thread: OPA2990

Hello TI experts, 

Can you inform us of the size of the internal pull down resistor on the shutdown pin of OPA2990S. We cannot design the external circuitry for driving this pins without this knowledge. 

Thanks a lot!

Best, Christian

  • Hello Christian,

    Think of the pull down resistor as being a current sink. The typical current is 500nA. So I suggest designing for driving 5uA at a voltage greater than 1.2V but less than Vs and less than 20V. This 10X typical value includes plenty of design margin. 

    If you have to have a term in ohms, use 1.2V / 5uA = 240 k ohms.

  • Christian,

    I tested some samples and the shutdown pin is a current sink as I expected (for most Vs and Vsd values). However the pin current is a little more complicated than that. The shutdown pin current is zero when Vs is zero. As Vs increase to about 2V the resistance of the shutdown pin dropped from open to 1M ohms (for low Vsd voltage). Above Vs = 2V the resistance of SD pin becomes constant (about 1Mohm for the samples). The fixed current sink level changes with Vs until Vs is about 3.5V then the fixed current sink becomes constant.

    Shutdown current vs voltage for Vs=0V, Vs=2.7V.  Six temperatures

    Shutdown current vs voltage for Vs=5V, 15V, 40V.  Six temperatures

     The design goal for 5uA at at least 1.2V and the design goal for 1.2V / 5uA = 240 k ohms is still good.

  • Hi Ron,

    Thank you very much for that extra confirmation and clarification. I cannot tell you have much I appreciate this. We do much appreciate this seriousness.

    Since I am in contact with you I will take the opportunity to recommend that you take a look a how the shutdown pin is defined. It is a negated shutdown input, indicating that the IC goes into shutdown mode when the pin is low. This is however not the case. So I would recommend that you remove the negation line above the shutdown pin name in the IC symbols to make it more clear. 

    The OPA2990 is indeed shutdown when then pin is high (not low).

    On the same topic we have been receiving different indications on when OPA2990SIDGSR will be ready for full production. First it was November last year, then Feb this year and now it seems to be delayed again. 

    Can I get you to check right at the source when they truly expect to release this for normal production and normal purchasing for running production?

    Thanks a lot again.

    Best, Christian 

  • Christian ,

    The negation line will be deleted. This correction is already in work. I will check on the release date estimate; that could take a couple days. 

  • Christian ,

    The end on April is the target for release to market.