LM73606: LM73606 question about when increasing the output current will lower the switching frequency?

Bob Lee62837

Mastermind 7230 points

Part Number: LM73606

Dear support member

My customer used LM73606.

I have a question about switching frequency behavior.

(Specification condition)
Vin：33V
Vout：24V
Iout：0A～3A
fsw：500kHz

(Situation)
Increasing the output current will lower the switching frequency.
（When Output current exceeds 0.7A over,switching frequency is lower.500kHz⇒250kHz.）

(Waveform①）
Iout：0.6A
Ch2：Output voltage
Ch3：Switching voltage
Ch4：Inductor current

(Waveform②）
Iout：3A
Ch2：Output voltage
Ch3：Switching voltage
Ch4：Inductor current

（Question）
Q1
Is this behavior normal?

Q2
Why does the switching frequency drop?

Best regard.
Bob Lee.

over 5 years ago

0 Ankit Gupta95 over 5 years ago

TI__Expert 4555 points

Hello Bob,

We don't expect this behavior. Please share your schematic and layout.

Please let me know whether you are using TI EVM or custom EVM for your experiment? If custom EVM, can you please try on TI EVM as well. Thanks!

Best Regards,
Ankit Gupta
Application Engineer

0 Bob Lee62837 over 5 years ago in reply to Ankit Gupta95

Mastermind 7230 points

Dear Ankit Gupta95,

Thank you very much for your answer.

This waveform is the waveform in the custom EVM.

As I would like sent schematic and layout,
Could you teach your private E-mail address?

Best regard.
Bob Lee.

0 Ankit Gupta95 over 5 years ago in reply to Bob Lee62837

TI__Expert 4555 points

Hello Bob,

My email Id : a-gupta1@ti.com, Can you please close this thread in this forum, so that TI won't monitor this thread any further on E2E forum. Thanks!

Best Regards,

Ankit Gupta

Application Engineer

0 Bob Lee62837 over 5 years ago in reply to Ankit Gupta95

Mastermind 7230 points

Dear Ankit Gupta95,

Thank you very much for your E-mail address.

I sent mail to your private-Email.
Could you check it?

I closed post.

Best regard.
Bob Lee.

0 Ankit Gupta95 over 5 years ago in reply to Bob Lee62837

TI__Expert 4555 points

Hello Bob,

I received your email and will reply to it shortly. Please close this thread here. Thanks!

Best Regards,

Ankit Gupta

0 Bob Lee62837 over 5 years ago in reply to Ankit Gupta95

Mastermind 7230 points

Dear Ankit Gupta and Arief,

Thank you very much for your answer.
I appreciate it very much.

Best regard.
Bob Lee.

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LM73606: LM73606 question about when increasing the output current will lower the switching frequency?