LM51561: Minimum Comp Clamp Voltage

Kuramochi Tadahiko

Guru 28715 points

Part Number: LM51561

Hi,

My customer is evaluating LM51561 on flyback topology.

There is the following description on the datasheet.

However, switching stops actually when COMP voltage achieves the minimum clamp pin.

What does the above sentence mean?

Best Regards,

Kuramochi

over 3 years ago

0 Brigitte over 3 years ago

TI__Guru 58215 points

Hello Kuramochi,

Is the feedback voltage in the customer application connected to GND?

Best regards,
Brigitte

0 Kuramochi Tadahiko over 3 years ago in reply to Brigitte

Guru 28715 points

Hi Brigitte-san,

Thank you for your reply.

Yes, they are tieing the FB pin to GND.

Best Regards,

Kuramochi

0 Brigitte over 3 years ago in reply to Kuramochi Tadahiko

TI__Guru 58215 points

Hello Kuramochi,

Thank you for this information. Can you please send some measurements for clarification?

Best regards,
Brigitte

+1 Julian Hagedorn over 3 years ago in reply to Brigitte

TI__Mastermind 20900 points

Hi Kuramochi-san,

The comp dynamic range is 1.2V to 2.4V, if comp hits the clamp, the part will not be able to regulate. The negative clamp is deactivated in flyback mode, since the opto coupler is pulling the pin low.

regards,

Julian

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LM51561: Minimum Comp Clamp Voltage