LM5176: Step up working well, but step down is not working.

Hi Nathan,

thank you for using our device.

Could you please share your schematic?

thanks,

Moritz

Hi Moritz,

This is my schematic.

Thanks,

Nathan

3108.lm5176.pdf

Hi Moritz,

Were the schematics in a format that was useful. We use Labcenter Proteus for our layouts.  The original design comes from Webench.

Thanks,

Nathan

Hi,

Has anyone got any ideas as I've had to park this job until we get some feedback.  Do I need to look at a different part?

We have prototypes x 3 made up at some expense - what should we do now?  Scrap them?

Thanks,

Nathan

Hi Nathan,

Thank you for using the LM5176.  I am reviewing your schematic and so far no obvious problem is found. The LM5176 seems to be the right choice for this application.  Can I bother you to monitor SW1 and SW2 when you see issue in output regulation?  

Thanks,

Youhao Xi, Applications Engineering

This is from SW2 at 32V:

And the next two are from SW1:

When we are below 28V input voltages, we get good delivery of output at 28V and also the SW1 / SW2 are clean: example below of operation below 28V:

Youhao Xi said:

Hi Nathan,

Thank you for using the LM5176.  I am reviewing your schematic and so far no obvious problem is found. The LM5176 seems to be the right choice for this application.  Can I bother you to monitor SW1 and SW2 when you see issue in output regulation?  

Thanks,

Youhao Xi, Applications Engineering