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LM5156: LM5156

Baraa Jarkas
Prodigy 10 points
Part Number: LM5156

Hi,

I want to design a sepic converter that generate 20V, 350mA using LM5156. The input range is 2V - 12V. Is this possible?
Because i tried to simulate this Circuit using Webench and then Pspice but it doesn't work.

Thanks
Baraa

  • 0
    TI__Genius 11215 points

    Hello Baraa, 

    Thanks for your message. I think in this case there might be two potential issues with your design. First, at the minimum Vin you might violate the max duty cycle spec, but this depends on the selected switching frequency too (please refer to Electrical characteristics table at page 7 and to Figure 8-16). On the other hand, with a minimum Vin of 2V, the device can operate if the BIAS pin is greater than 3.5 V (please refer to section 9.1 page 12). May I ask you why you selected a SEPIC topology for your desired specifications? I'm looking forward to your answer. 

    Kind regards,
    EM

  • 0
    Prodigy 10 points

    Hi EM,

    Thanks for your reply. It's just a Project requirment. Ihave already seen the datasheet, calculated the values using "Excel Calculator for SEPIC" and then connected the BIAS pin to 5V but the circuit still doesn't work.

    Best regards,
    Baraa

  • 0 in reply to Baraa Jarkas
    TI__Genius 11215 points

    Hi Baraa, 

    Thanks for your clarification. Do you get an error from the PSPICE simulator or do you just see that the circuit does not work as expected? Can you please share a screenshot of the message you get and of your schematic? What type of message is WEBENCH giving you?

    Kind regards,
    EM