LM5140-Q1: Oscillator frequency lower limit when Vin drops

Tomoaki Yoshida91

Part Number: LM5140-Q1

Hi team,

I'm considering to use LM5140-Q1 for dual separate power supply.

When the Vin drops, it is explained in the datasheet that the internal oscillator lowers the frequency to keep the output voltage.

It is not written frequency limits on the data sheet, but is the lower limit of frequency dropping defined?

And what happens when Vin drops beyond the limit of the output setting?

Best regards,

Tomoaki Yoshida

over 8 years ago

0 Terry Allinder over 8 years ago

TI__Expert 3545 points

Tomoaki,

Thanks for your question about the LM5140. The minimum oscillator frequency that the LM5140 will drop to when VIN falls is ~57 kHz. If VIN continues to fall below the Vouts regulation point, the controller will operate in a drop out mode were Vout will track VIN minus the IR drops, I’ve attached an example below.

Terry

0 Tomoaki Yoshida91 over 8 years ago in reply to Terry Allinder

Genius 5255 points

Hi Terry-san,

Thank you for your support.

It was very helpful for me.

Best regards,

Tomoaki Yoshida

Power management

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LM5140-Q1: Oscillator frequency lower limit when Vin drops