Portable Cell Phone Charger - few questions

[Pawni]

So what I'm trying to achieve is a charger that can be connected to a USB port from a PC for example, then it will charge a 3,7V 2000mAh Lithium Ion Battery with configurable 250mA-500mA current (set by a resistor on the PCB for MCP73831T).

Then the charger can be connected to a smart phone eg. N900 and it will supply it with 500mA.

The charger itself would have 2 different USB ports, one to charge itself (micro-B) and one that would allow devices to be charged from it (Type A) so basically I could flip the same charging cable around to charge my phone or eBook etc. device that has micro-B on it.

I'm having a few doubts though of making this work:

I've understood that for a device to draw over 100mA from USB it needs to be allowed to do so?
So I couldn't just hook the charger to my PC's USB port with D+ and D- floating and expect it to get 400-500mA of current from it?

And also for charging a device from the charger:
I've also read that some devices won't even charge from a USB that has D- and D+ floating, is this correct and how can this be fixed?
I'd remember a jumper of some kind between the lines.

If you have got any feedback about this I'd love hear it.
All help is respected

Thanks!

 

[Sceadwian]

Technically to draw more than 100ma the port must request it from the host, at least according to USB specs, this doesn't stop it from drawing more current but some hosts may shut down the port if more than 100ma is drawn, depends entirely on the host implementation. You do need to terminate the data lines on some phone's but it's phone dependent, not sure how it's done, probably just a resistor, Google should find you the info you need.

You don't just need a charger circuit though you need a regulator circuit for the output, because a phone won't charge straight from a Lithium source, the voltage needs to be higher, most cell phone's use 4.6-5.0 volts so you need a boost converter.

 

[KeepItSimpleStupid]

They load the data lines typically. Apple has some propreitary scheme so charger can deliver nearly 2A. See: https://www.electro-tech-online.com/custompdfs/2011/05/tps2540.pdf for some info.

Motorola phones won't charge at the high rate unless a Motorola Charger is used or a Motorola Data Cable is used.

 

[Pawni]

Technically to draw more than 100ma the port must request it from the host, at least according to USB specs, this doesn't stop it from drawing more current but some hosts may shut down the port if more than 100ma is drawn, depends entirely on the host implementation. You do need to terminate the data lines on some phone's but it's phone dependent, not sure how it's done, probably just a resistor, Google should find you the info you need.

You don't just need a charger circuit though you need a regulator circuit for the output, because a phone won't charge straight from a Lithium source, the voltage needs to be higher, most cell phone's use 4.6-5.0 volts so you need a boost converter.

Yes I know that, but it wasn't directly relevant to my question about the data lines so I forgot to mention about it.
I'm designing the charger circuit for the lithium and for the phone seperately so I can use the same PCBs on different projects that don't need both features.

I'm probably going to use something like Maxim's MAX1763 because it can be easily customized for many different scenarios.

They load the data lines typically. Apple has some propreitary scheme so charger can deliver nearly 2A. See: https://www.electro-tech-online.com/custompdfs/2011/05/tps2540-1.pdf for some info.

Motorola phones won't charge at the high rate unless a Motorola Charger is used or a Motorola Data Cable is used.

Hmm, I'll have to search something about that then or just experiment. Probably a small resistor can fix it.

You don't see many Motorolas phones here in Finland so that's not a problem (I've probably seen less than 10 people have one here).

 

[RCinFLA]

Motorola uses various value resistor on data lines, at the phone connector end, on their wall mount power pack to determine maximum charge current. You can find info on web.

They do this because some of their phones allow different capacity batteries. They rely on wall charger power pack to limit the maximum current so their in-phone series pass regulator transistor has less power dissipation. The can charge from a computer but they follow the USB negotiation protocol with host before they engage full current charging. They obey the 500 mA specs of USB spec when connected to host PC. Since USB does not have current limiting that matches phone, the phone will duty cycle charging on and off to keep the internal series pass charge regulator device from getting too hot.

 

[KeepItSimpleStupid]

Those resistors are located in their phone specific data cables too. That's why they have specific cables for specific phones.

 

[karaapak]

https://www.electro-tech-online.com/threads/can-we-charge-3-7-v-battery-from-usb.118660/#post975125
I had opened a topic about charging li-poly batteries with using usb port. In there I added some circuits and maxim' s IC for this application as you know maxim has wide variety IC's for regülators that may be helpful.

 

[Pawni]

https://www.electro-tech-online.com/threads/can-we-charge-3-7-v-battery-from-usb.118660/#post975125
I had opened a topic about charging li-poly batteries with using usb port. In there I added some circuits and maxim' s IC for this application as you know maxim has wide variety IC's for regülators that may be helpful.

Thanks for the link and all, but the charging of the LiOn/LiPo isn't my problem currently anymore. I'm going to use the MCP73831 to charge the battery from USB, but now I'm looking for an IC that can efficiently boost the voltage from 4,2V-3,0V to 5V @ 500mA.
Many ICs boost only to 100-300mA @ 5V but I've got a few listed that may suit my purposes. All the ICs I looked are from Maxim, TI had one really great IC for this but the packaging was a bit odd.

If you have any of these that you can recommend I'd really appreciate it too

 

[Sceadwian]

Did you try Linear Technologies? They have a great parametric search tool for their parts, if you can't find what you need from them I'd be surprised.
They support and distribute LTSpice free of charge, any company that does that gets my vote for a good look at their products. Best of all they provide LTSpice models for almost every regulator they produce, it's the reason for LTSpice's funding, it's a marketing tool for them to allow people to simulation their devices in a spice environment free of charge, anyone that plays around long enough will probably find a device in their repertoire that meets their needs.