LM43603 output current vs control mode

Hiroshi Sato

Expert 2590 points

Other Parts Discussed in Thread: LM43603, LM53603

Hello,

Our customer evaluating LM43603 for RF power amp supply.

They want to use this with CCM/DCM mode(=do not enter PFM mode) in all output current situation, from 100mA to 2A.

In their evaluation by EVM with 100mA to 2.5A load, it operates with PFM mode when the current lower than 250mA.

(Vin=24V+/-10%, Vout=3.3V, Fsw=1MHz)

The customer can change inductor and other external components, but we don't know the way to optimize them.

Can we check the relation between output current and switching mode with WEBENCH or any tool ?

Thanks and best regards,

Hiro

over 9 years ago

0 Marc Davis-Marsh over 9 years ago

TI__Genius 10115 points

Hi,

Webench does estimate the light load behavior and you can see the effect on the Efficiency curve. As the load current decreases you will see an inflection on the curve and the efficiency will start to flatten out.

At this point the part is lowering the frequency. You can calculate the entry point with different inductors. In general a lower inductor will lower the DC current of the light load entry point.

If this doesn't come up with a suitable solution, you can also try the LM53603 which has a FPWM mode that will disable the low frequency mode.

Regards,

Marc

0 Marc Davis-Marsh over 9 years ago in reply to Marc Davis-Marsh

TI__Genius 10115 points

0 Hiroshi Sato over 9 years ago in reply to Marc Davis-Marsh

Expert 2590 points

Hello Marc-san,

Thank you for your replying, I understand and

I'll inform the customer about that and ask to keep evaluating with different inductors.

Thanks and best regards,

Hiro

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LM43603 output current vs control mode