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Original question:

TLV704: TLV70433 5V to 3.3V overshoot issue

TLV704: TLV70433

Rishabh Rishabh
Prodigy 90 points
Part Number: TLV704
Other Parts Discussed in Thread: TPS709,

It looses regulation in Radio susceptibility at around 500 mhz. explain 

  • 0
    TI__Mastermind 23361 points

    Hi Rishabh, 

    In order for us to better understand the issue, will you share more details on the problems you may have seen or experienced with the LDO being affected by the 500MHz radio frequency?

    Regards,
    Jason Song

  • 0 in reply to Jason Song
    Prodigy 90 points

    I am using TLV74050 to power up MCU, so when I test it as per CE, then while testing RS ( 10 V/m ) @ around 500 mHz

    LDO loses regulation and voltage becomes 6.5 V at LDO output.

    I am using 10 mfd tantalum at output of LDO and LDO input is 13V ( Very well regulated smps output ) the layout guidelines are followed as per TLV74XXX datasheet.

    I suspect that RF freq injecting noise in ground which results in loss of regulation, 

    Earlier I was using lmxx series regulator that i replaced with TLV74050 and problem started.

  • 0 in reply to Rishabh Rishabh
    TI__Mastermind 23361 points

    Hi Rishabh,

    Thanks for your detailed feedback. Unfortunately due to the low ground current, this device is more suspetable to EMI. We have seen similar posts on other applications. See here: e2e.ti.com/.../665725

    At this moment, the best pin compatible solution is to replace the device to TPS709. TPS709B does have pin 5 as "enable pin" instead of "nc", but the "enable pin" can be left floating to enable the device. If you previously short the "nc" pin 5 to ground, you will need to change your layout to use TPS709B device.

    Regards,
    Jason Song

  • 0 in reply to Jason Song
    Prodigy 90 points

    Thanks

    But what is it sure that TPS709 will not have EMI problem.

  • 0 in reply to Rishabh Rishabh
    Prodigy 90 points
    and supposing if I put small inductor or resistor of few ohms then problem can be solved?
  • 0 in reply to Rishabh Rishabh
    TI__Mastermind 23361 points
    Hi Rishabh,

    It is important to note that EMI testing is generally done at a system level than at the LDO level so we do not have much data on any specific product. We more or less just know that low Iq parts are more susceptible and many customers have switched the TLV704 to TPS709 after running into EMI issues.

    Regards,
    Jason Song