LP8758-E0: VIN_Bx,SW_Bx,FB_Bx

Hi Yuto,

Will the one channel not be utilized at all? In a 3-phase + 1-phase configuration the inputs VIN_B0/1/2/3 are tied together. The output voltage in the 3-phase configuration is differential. Hence, FB_B0 is tied to the output VOUT and FB_B1 is tied to ground at the load to offer the proper return path. FB_B2 is tied to ground and FB_B3 is tied like a normal 1-phase configuration in single-ended feedback form. However, if you don't plan to use the remaining rail at all and just use the device in a 3-phase configuration with the other rail disabled then you should tie FB_B3 to ground to avoid any noise coupling into the pin. Since, VIN_B3 all have separate power pins and are not connected internally I don't see an issue with leaving this floating. However, let me confirm this and look into what should be done for the SW_Bx pin. Also, I have added a link to an application note that covers the various multi-phase configurations of the LP8758. Let me know if this helps.

http://www.ti.com/lit/an/snva737/snva737.pdf

-Raymundo Hernandez-Toscano

Hi Raymundo-san,

Thank you for your kind reply.

Our customer plan to use LP8758-E0 in four 1-phase configuration like Figure 4 of application note.

And VIN_B3, FB_B3 and SW_B3 are unused.

If 1 channel not be utilized at all, I think FB_B3 should be tied to GND, VIN_B3 and SW_B3 are floating,Is it right?

Best Regards,

Yuto Sakai