LM5156H-Q1: OUT PUT 12V Line Short

CHO SR

Genius 3265 points

Part Number: LM5156H-Q1
Other Parts Discussed in Thread: LM5156, LM51561H

Please answer the customer's questions.

1) What happens when OUT PUT 12V Line Short occurs?

(Recovery enabled?, Converter damaged? Maximum sustainable time?)

over 3 years ago

0 Garrett Roecker over 3 years ago

TI__Mastermind 21720 points

Hi CHO SR,

Thanks for reaching out with your question and for considering the LM5156 in your design.

What is the topology (Boost, Flyback, SEPIC) that the LM5156 is configured as? This will have an impact on the short circuit operation.

Thanks,

Garrett

0 CHO SR over 3 years ago in reply to Garrett Roecker

Genius 3265 points

Hi Garrett,

The configured topology is SEPIC.

I have attached a schematic for your reference.7713.LM51561H-Q1 schematic_201022.pdf

0 Brigitte over 3 years ago in reply to CHO SR

TI__Guru 59755 points

Hello CHO,

Please excuse the late response. The expert for this device is out of the office so it will take until next week to get a ensured answer.

I expect that the device is going into minimum on-time operation during the overcurrent event on the output. If the device overheats it will go into thermal shutdown.

0 Garrett Roecker over 3 years ago in reply to CHO SR

TI__Mastermind 21720 points

Hi Cho,

If the SEPIC configuration the output voltage will go to 0V when it is shorted. The COMP pin voltage will rise and the duty cycle will increase. As the duty cycle increased the peak switch current will increase until it hits the peak current limit. In the LM51561H there is hiccup mode current limit protection enabled. After the peak current reaches the peak current limit for 64 cycles the device will pull down the SS pin quit switching for 32768 cycles to keep the power train components from overheating. After that time the device will try to to restart and the SS pin will begin to rise. This will continue until the output short is removed.

Please let me know if you have any questions.

Thanks,

Garrett

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LM5156H-Q1: OUT PUT 12V Line Short