Electronics > Beginners
Power Delivery issues with boost converter
tyguy2:
Hello all,
I've recently designed a 5v rail that takes a minimum of 3.3v from a battery and steps it up to 5v, with a maximum current draw of 500ma (schematic attached, here's the part https://www.digikey.com/product-detail/en/maxim-integrated/MAX1522EUT-T/MAX1522EUT-TCT-ND/6680188). I'm already imbedded the design into a PCB, but I'm getting strange voltage sags when I try to draw anything over around 200ma. Does anyone have any ideas on how I can fix this without having to rerun a new PCB?
StillTrying:
I can't see anything obvious from the data sheet, are you sure the input 3.3V isn't dropping.
tyguy2:
I've checked that, and I'm not getting any issues with that either. 3.3v comes directly from a LiPo
Audioguru again:
Your 3.3V Li-PO is almost dead. It is 4.2V when fully charged and is 3.7V when half-charged. it should be disconnected and re-charged when it is 3.2V.
Are you drawing 5A from the 3.3V Li-PO? That is 5A x 3.3V= 16.5W. Maybe 1.6W is wasted on heat then the 5V output will be 15.5W/5V= 3.1A but a Li-PO that is almost dead cannot produce the original 5A.
tyguy2:
--- Quote from: Audioguru again on July 19, 2019, 02:05:30 am ---Your 3.3V Li-PO is almost dead. It is 4.2V when fully charged and is 3.7V when half-charged. it should be disconnected and re-charged when it is 3.2V.
Are you drawing 5A from the 3.3V Li-PO? That is 5A x 3.3V= 16.5W. Maybe 1.6W is wasted on heat then the 5V output will be 15.5W/5V= 3.1A but a Li-PO that is almost dead cannot produce the original 5A.
--- End quote ---
No, this Lipo is fully charged to 4.2v, I'm just having it operate down to the drop off voltage of the battery. I said I was drawing 500ma, not 5A.
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