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TPS2H160-Q1: Fail to pass conducted susceptibility

user6452651
Prodigy 50 points
Part Number: TPS2H160-Q1
Other Parts Discussed in Thread: TPS2H160EVM

Dear expert,

Our product containing several TPS2H160A-Q1 as power outputs fails to pass the conducted susceptibility test in the range between 250 KHz and 1.1 MHz.

To investigate the problem, I used the TPS2H160EVM board to reproduce the problem by injecting a 1 Mhz signal generator to the TPS2H160 output.

By injecting a sinus signal on the output, the TPS2H160 does not switch on and generate a fault, this seems act as a current overload. The problem occurs with frequency up to about 3 MHz.

Increasing the current (CL to GND) does little to improve the susceptibility. The power supply is good with decoupling capacitor.

A capacitor (5 - 10 nF) on the output improves a lot.

Do you have a workaround for this problem?

I insert a file with oscillo screen captures

TPS2H160EVM conducted susceptibility problem.docx

Regards

Jean-François

  • 0
    TI__Genius 13300 points

    Hello Jean-François,

    Welcome to E2E! What specific test are you running that requires a 1MHz signal with 5 Vpp to be injected? Lowering the output voltage from Vs will cause for a lot of energy to be dissipated across the device. Capacitors from Vs to ic_gnd (100 nF || 10 nF) and 100 nF from the output to system ground will help with EMC performance. 

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Prodigy 50 points

    Hello Kalin,

    It is the conducted susceptibility test, it tests the radio frequency immunity of a device. Instead of exposing device to radio frequency, the test consist to inject radio frequency directly on the input/ouput cable through capacitors or through an inductor. the test goes from 10 KHz to 400 MHz.


    The IC is good decoupled with 10 uF || 100 nF. I can't put 100 nF on the output because I need maximum rise/fall time, these outputs are also used to send data... So I can put only few nF on the output and each susceptibility test costs a lot... So if you have an other tips to resolve this problem, I'll take it !


    The energies send through this 1 MHz singal is far less that the IC can drive. If the IC is already switch on, there is no problem, but while ramping up the IC drives less current than it should, even no current. The signal seems disturb the internal IC circuitry...

    regards

    Jean-François Herminjard

  • 0 in reply to user6452651
    TI__Genius 13300 points

    Hello Jean-François,

    Our device has a controlled slew rate so a 100 nF capacitor from output to ground should not be noticeable and should solve your issue.

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Prodigy 50 points

    Hello Kalin,

    My main issue is the falling time (switch off) and I can have very weak loads...

    But it is quite obvious that this IC needs a decoupling cap on its output to pass EMC tests.

    Thank you for your help

    Regards

    Jean-François Herminjard