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LM5025: Abnormal oscillation caused by overcurrent detection of CS1 pin

Kaji@PAN

Mastermind 7795 points

Part Number: LM5025

Hi,

I am studying a circuit using the LM5025 device.
In my circuit, when the overcurrent is detected by the CS1 pin, the switching frequency becomes abnormal.
This phenomenon occurs when the input voltage decreases (17 V or less).
So I don't think it's the RAMP pin effect.
What is the cause of this abnormal oscillation?

Best regards,

over 5 years ago

0 John Griffin1 over 5 years ago

TI__Mastermind 34465 points

Hello Kaji@PAN,

What are these two waveforms ?
One has a scale of 1A/div and the other is 20V/div

Your circuit is not complete. Are any of the other pins connected ?

The CS1 input is a cycle by cycle current limit. Its purpose is to terminate the OUTA when CS1 exceeds 0.25V.

If you wish to check this function then you should probe CS1 and OUT_A.

Is it possible to do this ?

Regards

John

0 Kaji@PAN over 5 years ago in reply to John Griffin1

Mastermind 7795 points

Thank you for your reply.

I plan to measure CS1 and OUT_A.
By the way, is there a calculator for this device?
This device does not have WEBENCH.

Best regards,

0 John Griffin1 over 5 years ago in reply to Kaji@PAN

TI__Mastermind 34465 points

Hello,

There is no calculator available for this part

Regards

John