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TPS65400: about internal Rvrm and Lvrm

Part Number: TPS65400

Hi,

Could you tell me about TPS65400 internal Rvrm and Lvrm spec?
Customers want that information for Altera's PLD tool.
Could you give me a reference value for entering into the tool?
I understand this value as information based on the internal error amplifier.

I will describe the tool information below.
www.altera.co.jp/.../ug_dev_specific_pdn_20.pdf

Best Regards,
Yusuke/Japan Disty
  • Hi,

    Could you expain what is the Rvrm and Lvrm?

    and What is the meaning of VRM?

  • Zhao-san,

    Thank you for your response.
    Customers want Rvrm=ESR and Lvrm=ESL information inside the device.
    (VRM=device internal ESR and ESL spec)
    Becouse,Customer needs to input the output impedance information to the simulation tool.
    (Enpirion has modeled this information.)

    Best Regards,
    Yusuke/Japan Disty






  • Hi,

    Sorry, i have no idea about the Rvrmand Lvrm.
    I will ask colleague.
  • Zhao-san,

    Thank you for your support.
    I will be waiting for your response.

    Best Regards,
    Yusuke/Japan Disty

  • Hi, Yusuke

    1. For Rvrm,

    Record ideal power voltage is Videal, output volage Vo1 @ I1, Vo2 @ I2.

    Videal - I1 * Rvrm = Vo1        (1)

    Videal - I2 * Rvrm = Vo2        (2)

    (1)-(2) equation, then Rvrm=(Vo1-Vo2)/(I2-I1)  

    So We can calculate Rvrm from load regulation test result. (See page 59 of datasheet).

    Under different Vout, the Rvrm is different, and it could be negative resistance.

    2. For Lvrm,

    According to equation: deltaV=L*di/dt,

    The L=deltaV/(di/dt)

    The di/dt is the slew rate of load current, the deltaV is the Vout changes during load transient.

    Using different di/dt and Co, the deltaV will be different.

    So you need to calculate the Lvrm according to your SPEC.  

  • Zhao-san,

    Thank you for your kind support.
    I understood the your explanation of Lvrm.

    One more thing "1.Rvrm".
    I can not understand the explanation below.
    Why did you (1) minus (2)?

    "Record ideal power voltage is Videal, output volage Vo1 @ I1, Vo2 @ I2."
    "Videal - I1 * Rvrm = Vo1        (1)"
    "Videal - I2 * Rvrm = Vo2        (2)"
    "(1)-(2) equation, then Rvrm=(Vo1-Vo2)/(I2-I1)"  


    Best Regards,
    Yusuke/Japan Disty

  • Hi, Yusuke -san

    It is just mathematical calculation.
    There are two unknown variable(Videal and Rvrm) and two equations.
    (1) minus (2) can cancel Videal, and derive Rvrm.

    In short, the Rvrm can be calculated by the load regulation.