• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 21 subscribers
  • Views 339 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2491: Input signal while Vcc is 0V

Sunset
Genius 13995 points
Part Number: LMX2491
Other Parts Discussed in Thread: CDCLVP1212,

Hello Team,

can you confirm/clarify the following point out of the table below:

  • Is the RF input pin an I/O input? Or I/O input means only logic signal input?
  • Before power supply(Vcc) turns on, is it possible to apply any signals into I/O pin? Because it beyond (Vcc (0V) + 0.3V) specification.
  • If I have an RF signal on the input will I have problems

Same questions for the CDCLVP1212, if I have the RF signal and Vcc is 0V, do I have problems?

If there are problems we need to think about powering up the last device in the clock chain first and than one after the other till the RF source.

Thanks,

SunSet

  • 0
    TI__Mastermind 33710 points

    Hi SunSet,

    • RF input pin is an I/O pin for the purposes of Abs Max ratings.
    • Applying a signal to the I/O pin before the power supply turns on is not recommended if it exceeds ±0.3V. There are ESD structures connecting the RF inputs to the supply rails.
    • RF signal on the input, as long as it's small (<±0.3V), shouldn't cause problems. Larger signals can cause problems and should be gated before the LMX2491 is powered up.
    • CDCLVP1212 has slightly different rules:
      • ±0.5V instead of ±0.3V
      • There is an input current limit of 20mA on CDCLVP1212. As long as the input current limit is obeyed, larger signals are permitted (with the expectation that the larger signals will be clamped to lower voltages by limiting the current to <20mA).

    Many RF sources come with an enable pin, or else can be powered from an LDO with an enable pin.

    Regards,

  • 0 in reply to Derek Payne
    TI__Genius 13995 points

    Thanks for the info,

    SunSet