Electronics > Projects, Designs, and Technical Stuff
Boost converter + lipo charger/battery protection circuit
aiq25:
--- Quote from: KL27x on March 18, 2019, 04:58:10 am ---Ok. Then I suspect that is either the soldermask or paste layer. Curious that it is the same color as the top copper layer!
--- End quote ---
This is weird. They are rendered as being part of the pad but I can't figure out what they actually are. I ran DRC again and everything was clear, so I'm not sure what they are. Attached is an 3D rendering.
PeterZ:
--- Quote ---This is weird. They are rendered as being part of the pad but I can't figure out what they actually are. I ran DRC again and everything was clear, so I'm not sure what they are. Attached is an 3D rendering.
--- End quote ---
That's how KiCad is showing the net/pad clearance. Not to confuse with pad to zone clearance, which might be different.
aiq25:
--- Quote from: PeterZ on March 18, 2019, 01:37:09 pm ---
--- Quote ---This is weird. They are rendered as being part of the pad but I can't figure out what they actually are. I ran DRC again and everything was clear, so I'm not sure what they are. Attached is an 3D rendering.
--- End quote ---
That's how KiCad is showing the net/pad clearance. Not to confuse with pad to zone clearance, which might be different.
--- End quote ---
Thanks. I will clean up the PCB to avoid the clearances.
aiq25:
I started cleaning this up a little but I think there is no point, I'm going to get this PCB made and then change the design to use one of the TI IC's with integrated boost. That way I can have boost plus charging all in one IC.
janoc:
--- Quote from: aiq25 on March 18, 2019, 06:19:06 pm ---I started cleaning this up a little but I think there is no point, I'm going to get this PCB made and then change the design to use one of the TI IC's with integrated boost. That way I can have boost plus charging all in one IC.
--- End quote ---
Uh careful - those BQxxx chips only provide a USB OTG boost converter function (aka if you activate the function, you will get 5V/1A out of the normally input Vbus pin to power any device that could be connected to e.g. a smartphone). Otherwise they work as a sort-of buck converter when you have charger connected. If the battery is too discharged or not present the IC will regulate the output voltage to about 3.5V minimum, otherwise it keeps the output at battery voltage + 150mV (or so) - so the output is not really regulated and moves as the battery voltage changes. When running without the charger, the output isn't regulated at all, i.e. no buck or boost functionality (ignoring the OTG thing).
The datasheet is a very confused mess with quite a few contradictory parts but when you look at the block diagram of the IC it is clear what it can actually do.
If you need regulated output (boost converter), you will need to either use the OTG function (may not be practical) or add a separate converter. Basically these chips are meant to be fast USB chargers supporting OTG power and managing the power path in such way that it balances both the charging of the battery and powering the output in various charger/battery combinations. Nothing more, really.
That is unfortunate but it kinda makes sense given these are meant for smartphones and similar applications, where you will need to generate multiple power rails anyway. So it doesn't try to be smart and get in the way (which would only waste power) - it only handles the battery charging for you and delivers a meaningful (not necessarily stable or regulated) voltage that you can then convert further, as needed.
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