LM51551: Boost configuration not working

Takuchi

Intellectual 270 points

Part Number: LM51551

Hello,

I'm trying to design a 100V boost converter using this LM51551 and it's just not working for me.

The conditions are:

Input: +12V
Output: +100V @ 0.3A

Symptoms:

When I plug in the lab power supply, the input voltage drops and the lab power supply ramps up to full current capacity (like it's being short-circuited). I measure the resistance between Input and GND and it's about 490Ohm.
I took out Q3 and D1 to measure the internal voltage regulator:
- Vrt = 0.5V (at pin 10)
- Vcc = 6.85V (at pin 2)
I also changed R14 to 0R, nothing changes.

This is my schematic:

This is the Power Bench Designer reference: https://webench.ti.com/power-designer/switching-regulator/customize/19?noparams=0

Am I doing anything wrong here?

Thank you very much in avdance.

Best Regads,

over 2 years ago

0 Moritz over 2 years ago

TI__Genius 16015 points

Hello,

Thanks for reaching out. Your schematic looks OK. Do you use an EVM or do you have your own design?

490 Ohm between Input and GND is too low. Can you change the IC to exclude the possibility it is damaged? We are looking forward for your response.

Kind regards,

Moritz

0 Takuchi over 2 years ago in reply to Moritz

Intellectual 270 points

Hello, thank you for your response.

I'm using my own design :). I'll try exchanging the IC and comeback with the result

0 Takuchi over 2 years ago in reply to Moritz

Intellectual 270 points

Hello,

I exchanged the IC, still it does not work :( any other possible causes?

0 Moritz over 2 years ago in reply to Takuchi

TI__Genius 16015 points

Hello,

Can you try to use a power supply that is able to deliver a higher current? I that not helps, can you please send scopeshots of the input voltage when turning on, as well as the output voltage, the SS pin and the FB pin please? We are looking forward for your response.

Kind regards,

Moritz

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LM51551: Boost configuration not working