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TPS563201: The transition point to the light load operation

Part Number: TPS563201
Other Parts Discussed in Thread: TPS563208

Hello experts,

I got question about the transition point to the light load operation from customer.
From equation of IOUT(LL) in datasheet P10, we can calculate the transition point.

For this equation, we need frequency value.

Can we figure out the frequency value from WEBENCH's chart?

Or should we utilize figure 7 in datasheet?

Are these correct way?

Thanks and best regards,

Ryo Akashi

  • Akashi-san,

    You can use datasheet figure 8 or we bench to estimate the efficiency during light load operation.  Figure 7 is for TPS563208 which operates in forced PWM mode where the frequency does not reduce in light load conditions.

  • Hello Tucker-san,

    Thank you for your reply.
    I'm sorry, I misunderstood about figure 7. It shows about fSW vs Vin for TPS563208.
    Let me ask additional question.
    From figure 8, we can estimate the transition point (IOUT(LL) and fSW). Is it correct?
    My customer wants to know the switching frequency value which we can apply for equation (1) in datasheet.
    The customer's condition (Vin, Vout, Iout) is different from datasheet shows. It's difficult to apply the data from figure 8 directly.
    Could you give me advise how to estimate switching frequency for equation (1)?
    Thanks and best regards,
    Ryo Akashi
  • Hi Ryo,

    Use typical center frequency of 580kHz to calculate the transition point through eq1. Attached a calculator as below to calculate the real fsw under light load conditions.

    Fsw_ECO_DCAP2.xlsx

  • Hello Ryan,

    Thank you for your reply.
    I understand the frequency value.
    Also, thank you for sharing calculator.
    Thanks and best regards,
    Ryo Akashi