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Original question:

TAS5825M: Inductor-Less operation

TAS5825M: TAS5825 edge rate control and power consumption when using ferrite bead

Kazuki Kuramochi
Genius 10525 points
Part Number: TAS5825M

Hello,

My customer has 2 question for TAS5825M.

The first, Previous thread described TAS5825M has Edge rate control. However this function is not described by datasheet. Could you explain about it?

The second, my customer observed increasing idle current when use ferrite bead. and They would like to know how to minimize the quiescent current when use ferrite bead. Could you tell us that what parameter is dominant for quiescent current. And do you have the recommended filter value for minimizing idle current?

Best regards,

Kazuki Kuramochi

  • 0
    TI__Expert 6295 points
    hi, Kazuki,

    edge rate is fixed by OTP, it is not open for customer programming.

    idle current impacted by lots of parameters like PWM Freq, modulation mode and LC /ferrite bead selection. what is your customer application PVDD? normally we propose 1SPW mode for lower idle current. normally we proposed 384K, hybrid mode/1SPW mode, 10uH+0.68uF to achieve around ~23mA idle current.
    refer to below apps note about idle current: www.ti.com/.../slaa836.pdf
  • 0 in reply to Xiaolin Qin
    TI__Genius 10525 points
    Hi Xiaolin-san

    Thank you for your prompt reply.

    As for edge rate control, Does TAS5825's edge-rate control reduce the edge-rate than the other DAMP which doesn't support inductor free operation?

    Your provided document don't described the case of using ferrite bead. Could you provide any documents or information for reducing idle current when using ferrite bead?
    Our customer concern is that they observed the phenomena of increasing idle current when comparing 10uH/0.68uF output filter and ferrite bead output filter. So I would like to get the information for output filter using ferrite bead.
  • 0 in reply to Kazuki Kuramochi
    TI__Genius 10525 points
    Hi Xiaolin-san,

    Do you have any update for this?

    Best regards,
    Kazuki Kuramochi
  • 0 in reply to Kazuki Kuramochi
    TI__Expert 6295 points
    hello Kazuki-san,

    mostly slow down edge rate could some help for inductor free EMC. but also need to balance class-D dead time to escape device damage. I will send you by email of data studying of idle current between different Fsw, inductor and modulation mode selection for your reference.
  • 0 in reply to Xiaolin Qin
    TI__Genius 10525 points
    Hi Xiaolin-san,

    Thank you for your great information.
    It's make clearly understanding of the deference each modulation in the case of ferrite bead!

    By the way, App report of SLAA836 described that Increasing the inductance of the coil is effective for reducing power consumption. is it apply for ferrite bead case as well?
    Our customer would like to know how to chose the ferrite bead output filter's components for low power consumption.