• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 132 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

UCC28911: Guard the VS-Pin against EMI

Roland Melad
Intellectual 1185 points
Part Number: UCC28911
Other Parts Discussed in Thread: LM46001

Hi team,

We got an inquiry from our customer as below. Any recommendations we can provide?

The power supply is for a motor drive with IGBT power stage.

The required currents are:
Vcc1=18.5V@<50mA Gate voltage for the IGBTs.
I24V=27V@<200mA input to LM46001 synchronous step down converter to 5V.

The problem is not the output power.
I think the problem is the coupling from the power stage (10kHz max. 400Vpp) to the VS-pin (distance 3cm).
If i shield the VS-Pin there is no problem.
Is it possible to guard the VS-Pin against EMI and how can i do this?

Regards,
Roland

  • 0
    TI__Mastermind 25570 points

    Hello Roland

    Electric field screening is much easier than magnetic field screening so here are some ideas. The one on the left would be more effective than the one on the right.

    Adding some capacitance to Ground from the VS line is difficult because this pin needs to have a good high frequency response so I'd suggest leaving that idea aside for now.

    The VDD pin lies between the VS and drain pins of the device - the VDD pin can be used as an ac ground to screen the VS signal in the same way as the Ground line shown above. This may be easier to do on the PCB.

    There is also the possibility that the 400V signal is un-necessarily noisy due to stray inductances in the switching paths - for example voltages generated across the ground paths may add to the signal seen by the controller at the VS pin - although, if screening is effective this may not be the root cause.

    Please let me know how the customer gets on.

    Regards

    Colin

  • 0 in reply to Colin Gillmor
    TI__Mastermind 31580 points

    Hi Roland,

    It has been over a week since Colin's response and I hope you have made some progress in the meantime.

    I am going to close this post. Please open a new post if you have more questions.

    Regards

    Peter