LM43601: Negative output issue

Mason Noh

Expert 2490 points

Part Number: LM43601

Hi TI,

I have designed -5V Inverter design based on Webench simulation. But It's not working(No output).

This issue is solved when I removed the capacitor is from VIN to VOUT (Cio) or reduced to under 0.1uF

Load current is under 100mA.

Please let me know about the reason.

The voltage rating of Cio is over 25V.

0 Andy Chen over 5 years ago

Hi Mason,

What's the input voltage range so we can verify the Webench design?

Normally Cio 0.1uF is good enough for this topology.

0 Mason Noh over 5 years ago in reply to Andy Chen

Expert 2490 points

Hi Andy,

Input voltage is 5V.

If Cin value is too large, can it not work?

0 Andy Chen over 5 years ago in reply to Mason Noh

Hi Mason,

Cio and Cout Pls will divide input voltage, if Cio is too big, LM43601 may see high enough voltage for startup.

Pls measure voltage between Pin13/14 and Pin15/16 by oscilloscope at Vin turn-on, it should be higher than 3.8V for chip startup.

0 Andy Chen over 5 years ago in reply to Andy Chen

Hi Mason,

Pls ignore above reply.

Cio and Cout will divide input voltage, if Cio is too big, LM43601 may NOT see high enough voltage on Cio for startup.

Pls measure voltage on Cio by oscilloscope at Vin turn-on, it should be higher than 3.8V for chip startup.

0 Mason Noh over 5 years ago in reply to Andy Chen

Expert 2490 points

Hi Andy,

Thank you for your kind support.

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