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LMR61428: Lmr61428 boot strap issue

Part Number: LMR61428

Dear sir ,

I am not able to achieve boot strap operation in sample circuit mentioned in you detail document-SNVS815 on page no. 2& 12. But I m getting good result of boot strap in evaluation module i purchased from TI company.

please find the attached copy of 

please help me, and check error in my PCB layout ckt.



  • Hi,

    I would suggest that you enter the parameters on the webench for VIN, VOUT and IOUT and it will calculate the required components for you

    Go to the right hand side of the website above and there is a webench calculator for you

    As for layout, could you forward your schematic so that i can double check where the components go?



  • Looks like your PCB will pass a DRC for netlist connectivity but attempting a SMPS design with a single sided approach is a challenge as you are finding. The ground paths from IC pins 1 and 5 to the input and output capacitors must have the highest priority for being short and direct followed by the path through the inductor and diode and then make sure the trace to the Feedback Input is short, small and not routed near the switch node of pin 8. Using through-hole aluminum electrolytic caps without additional SMT ceramic caps bypassing them will also challenge the design.