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I'm designing my first PCB, a wireless Keypad/Macropad with a battery. I'm probably going to be using a 2Ah Li-Ion battery because there will be a lot of LEDs on it and I just want it to last longer but I'm not sure how exactly would I charge it over a USB-C port on it.

I'll be charging the battery at 1C (2A) and 5V from USB using a Li-Ion charging IC but I'm not sure if I need any special circuitry to enable that, do I need USB-Power Delivery for 10W or not? I'd also want to be able to charge it from a regular PC USB port (so 5V at 500mA or 900mA on USB 3 apparently) so how exactly would that work with USB-PD if I'll need it? Would USB-PD just use max. current it can get from the source even though it's not what it's trying to negotiate?

I've been researching this topic quite a bit in last few days and I've came across the TPS6598x IC series and I'd probably end up using that in case I need USB-PD so that's what this question is based around.

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  • \$\begingroup\$ Seems like there are two separate questions in here: one related to selecting the appropriate USB power specs for your load, and another related to recharging the battery once you have a local power rail. I'd suggest editing your question to highlight these separate requirements, or possibly making a separate question for each. \$\endgroup\$ – Chris Fernandez May 28 '19 at 16:51
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    \$\begingroup\$ I'm mostly interested in the USB power spec part, I haven't looked into battery charging enough but that should be simple once I have proper power input. I'll try editing the question to make this a bit clearer. \$\endgroup\$ – nufflee May 28 '19 at 17:08
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Your power requirements are well within the standard capability of Type-C port that uses special (but simple) pull-up resistor value on CC pins. The standard Type-C power delivery is 5V at 500/900 mA, (56k pull-up), 5V at 1.5A (if host pullup is 22 k, and 5V at 3 A id the pull-up is 10k. Therefore, completely forget PowerDelivery, and just use one of simple "CC controller" chips that usually detect the CC pulups, and can detect Chinese (DCP) port signature (D+ shorted to D-) allowing 1.5A.

There are also some charging chips that combine all features in one IC, look for recent additions to Texas Instruments BQxxxxx chips portfolio. These chips will scale its current intake depending on signature they see from USB port, all automatically.

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  • \$\begingroup\$ Thank you so much for the answer. I just have a few question, do I need a special kind of USB power supply that has these pull-ups or is that a part of USB spec and is included in pretty much any power supply? And if it is a part of USB spec, is it a new addition or not, ie. does it work with older chargers/power supplies and USB 2.0 (if not I guess the IC would just fall back to 500mA or something but that would depend on the controller probably)? \$\endgroup\$ – nufflee May 29 '19 at 1:05
  • \$\begingroup\$ And what was the IC from the BQ series you were thinking about? Is it BQ25713? \$\endgroup\$ – nufflee May 29 '19 at 2:10

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