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TPSF12C1: Saturation conditions for TPSF12C1

Conor
Guru 12155 points
Part Number: TPSF12C1
Other Parts Discussed in Thread: TIDM-1007

Tool/software:

Hi,

We are currently evaluating your active EMI filter product "TPSF12C1" and would appreciate your input on the following technical questions.

[Question 1]
In the evaluation results of TIDM-1007, the conditions for using an active EMI filter include "8.8uH DM Inductor."

Does this imply that unless differential mode (DM) noise is sufficiently attenuated using a DM choke (e.g., 8.8uH), the overall conducted noise (CM + DM) reduction with the AEF becomes ineffective, even when common-mode (CM) chokes are reduced?
Additionally, would you consider using a DM inductor more effective for DM noise suppression than simply increasing the capacitance of the X capacitors?

[Question 2]
According to the TPSF12C1 datasheet, the linear operating range of the INJ pin is specified as 2.5V to VDD–2V.
Assuming VDD = 12V, if the INJ voltage falls below 2.5V or exceeds 10V, we understand that the internal amplifier may be entering saturation.
Conversely, if the INJ voltage remains within this range, can we assume it is operating linearly and providing valid cancellation output?
Based on this understanding, we consider waveform ① to indicate saturation, while waveform ② appears to be within the linear operating range.

Could you please confirm if our interpretation is correct?

Best regards,
Conor

  • 0
    TI__Expert 5835 points

    Hi Conor

    I received your questions. I will get back to you as soon as possible

  • 0 in reply to Naresh Adepu
    TI__Expert 5835 points

    Question1: Yes, AEF only works in common mode dominant systems. If the system has dominant DM noise - then it doesn't respond. In such cases, we recommend adding a DM choke to filter the DM noise component. 

    DM noise can be filtered using both ways - either using a DM inductor or by increasing the value of X-capacitors. Both are effective. But increasing X-caps beyond a point, they become huge and bulky. that's why we end up adding DM inductor. 

    Question2: yes Conor, your interpretation is correct

    Thanks and regards,

    Naresh