LM43601: Waveform at the time of VIN re-input of LM43601 circuit

Masami Michino

Part Number: LM43601

Dear, All

Customers evaluate using LM43601.
They evaluate the instantaneous interruption of the input voltage, but when the VIN changes as follows, the occurrence frequency is low but problems may occur.
They set the output to 5V.
- VIN
28V -> 3V -> 28V -> 3V
- VOUT
5V -> 2.5V -> 26V -> 5V -> 2.5V

When VOUT rises to 26V, SW seems to be fixed to the input power supply ON.
We want to know why such a phenomenon occurs.
Please tell me what kind of condition the LM43601 will cause this phenomenon to occur.

The waveforms at the time of normal operation and abnormal occurrence are shown below.

Yellow - Output of regulated power supply
Blue - VIN
Purple - VOUT
Green - SW
10V/div,100mS/div

Normal

Abnormal

Thanks, Masami M.

over 5 years ago

0 Timothy Hegarty over 5 years ago

TI__Mastermind 49397 points

Hi Masami,

I forwarded your enquiry to the product expert. My understanding is that there's another open thread on this topic.

Regards,
Tim

0 Masami Michino over 5 years ago in reply to Timothy Hegarty

Genius 5070 points

Tim-san,

Thank you for your support.

Thanks, Masami M.

0 Masami Michino over 5 years ago in reply to Timothy Hegarty

Genius 5070 points

Tim-san,

Thank you for your support.
Please tell me about the situation surveyed by the product expert about this case.
There is no new writing even if you look at the following thread.
- 'LM43601 question on the output voltage rise at the time of input voltage fluctuation.'

Thanks, Masami M.

0 Robert Blattner over 5 years ago in reply to Masami Michino

TI__Expert 6165 points

Hello Masami,

I am sorry for the late reply.

I have asked around and found that this is not behavior expected from a working LM43601. I will continue asking around tomorrow. In the meantime, could you please send the following information:

1) A schematic
2) How often parts are abnormal (good # vs. abnormal #)
3) If an abnormal part is replaced on a PCB, is the circuit OK

If any of this information should not be on a public forum, please send by email to robert.blattner@ti.com and ambreesh@ti.com.

Regards, Robert

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LM43601: Waveform at the time of VIN re-input of LM43601 circuit