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LMX2430: Maximum current in clamping diodes

Part Number: LMX2430
Other Parts Discussed in Thread: LMX2485, LMX2491

I need to drive the LMX2430's Reference input hard such that the voltage exceeds 3.25V.  I protect the input with a 1K resistor to limit the current to less than 5mA.  Is this enough resistance to protect the part?  I couldn't find a spec on the datasheet for the maximum current.

  • Dan,

    I do not feel too good about this. The maximum input sensitivity is 0 dBm, and this is way higher than that.
    The maximum input ratings do say 3.25 V, but the recommend operating conditions are 2.75 V max.

    For another device on this process, I recall when a customer tried to push us to make it run to 3.0 V. If memory serves, I think that this reduced our long term reliability from 10 years to 1 year. So in other words, running at 3.25 V might work, but there would be concerns about reliability.

    Is there any reason that a resistive divider can't be used?

  • I’m actually trying to use the LMX2430 as a prescaler since so many prescalers are going obsolete. I want to try to maximize the dynamic range the reference prescaler works and the clamping diodes allow me to push the upper end of the dynamic range the device works over.

    I could increase the series r to limit the current even more. Most logic devices and uP have a input current rating on their inputs, but I couldn’t find a rating for this part.

  • Dan,

    Unfortuately, we don't have all this information for this part. This device has a 0 dBm max limit. Be aware we have other devices, like the LMX2485/86 or LMX2491 that can accept higher input power levels.