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TPS7A8300: Feedback loop connection consult

Stanley Dai
Expert 5810 points
Part Number: TPS7A8300

Hi Team,

Customer wants to check with us whether TPS7A8300's feedback pin can be connected behind magnetic beads? Pls help us here, thanks.

B&R

Stanley

  • 0
    TI__Mastermind 18466 points

    Hi Stanley, 

    are you using the Magnetic Bead as the pull up resistor for the PG pin connection?

    Best,

    Juliette

  • 0 in reply to Juliette
    TI__Expert 5810 points

    Hi Juliette,

    No, I mean SNS pin is connected with load behind magnetic bead? is that okay?

    Best,

    Stanley

  • 0 in reply to Stanley Dai
    TI__Mastermind 18466 points

    Hi Stanley, 

    What frequency is the ferrite bead rated for? Depending on that frequency and the bandwidth of the LDO, you may be able to use it. 

    Best,

    Juliette

  • 0 in reply to Juliette
    TI__Expert 5810 points

    Hi Juliette,

    Sorry, I am not quite understand your comments. Can you further explain the relationship between frequency of ferrite bead and bandwidth of our LDO? Thanks.

    Best,

    Stanley

  • 0 in reply to Stanley Dai
    TI__Mastermind 18466 points

    Hi Stanley, 

    There are a couple things you need to consider when choosing a ferrite bead, 
    1. There is a voltage drop across the bead
    2. They can be modeled as an inductor and a capacitor, but don't act like a low-pass filter - They choke off a very narrow frequency band for noise suppression. Depending on the rating of your ferrite bead and any load transients you may have, the ferrite bead may impact the response time of your LDO. 

    - This also means the device may become unstable. 

    3. Ferrite beads dissipate the noise they filter as heat. Depending on your load current, noise frequency, and enclosure, this may increase the ambient temperature surrounding the LDO and impact performance. 

    Considering all these points, it is recommended you do not connect a Ferrite bead on the feedback loop. 

    Best,

    Juliette