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# TLV62568: PFM knee

Part Number: TLV62568

Hi team,

I have a question about Figure 12 on the datasheet. It shows the knee of VOUT=1.2V is around 0.25A, and 2.5V is around 0.15A, although IL reaches 0A when 0.14A at VOUT=1.2V, 0.2A at VOUT=2.5V respectively. I think it is opposite because delta_IL at VOUT2.5V should be larger than VOUT1.2V. If it's not true, please let me know the reason why.

Regards,
Kazuto

• Hi Kazuto,

Can you please elaborate more on this:

"although IL reaches 0A when 0.14A at VOUT=1.2V, 0.2A at VOUT=2.5V respectively. I think it is opposite because delta_IL at VOUT2.5V should be larger than VOUT1.2V "

Please let me know what do you mean by the above statement. It would help me to answer you better. Thank you!

Best regards

Sneha

• Hi Sneha,

I mean the IL waveform below. Input the same condition to Power Stage Designer then I got the point when IL_min reaches to 0A.

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Regards,
Kazuto

• Hello Kazuto,

The area marked in red below shows an approximate threshold load current value when the PWM to PFM transition occurs.

The IL should be continuous in PWM mode and discontinuous in PFM mode. In PFM mode, IL (min) should reach zero. So, are you trying to simulate this transition using the power stage designer?

Best regards

Sneha

• Hi Sneha,

Please see my previous post. The load current when IL(min) reaches to zero is different for each output voltage. With VOUT=1.2V, Load=0.14A is the point. With VOUT=2.5V, Load=0.2A, according to the power stage designer. However on Figure 12, the plot for VOUT=1.2V enters PFM from larger current than VOUT=2.5V. I wanted to ask why it is opposite result compare to the calculation.

Regards,
Kazuto

• Hi Kazuto,

I will give you a feedback on Monday.

Best regards

Sneha

• Hi Kazuto,

The behaviour shown in the datasheet is tested and validated data specific for the TLV62568. Therefore, I would suggest to consider the data shown in the datasheet. I say this as the power stage designer might not consider the variations in the switching frequency wrt load current, the ON/OFF cycles etc. that are characterized by the device behaviour.

Please let me know if you need further help.

Thanks!

Best regards

Sneha

• Hi Sneha, I understood. Thanks for your support!