Hello TI community,
I'm designing a portable mobile phone/USB device charger using the TPS63002 chip to boost a 3.7V 2600mAh lithium ion battery (capable of producing up to 2A) to 5.0, then using the TPS2511 to put the device-specific voltages on the D+ and D- pins. Using a power supply, I've successfully tested my design with a couple of devices, including an iphone5. The iphone5 initially uses 1A or more of current from the power supply, then backs off to somewhere around 550-800mA. Note that this is read from the power supply.
However, when I switched to the lithium ion battery, iPhone charging initially works fine, pulling roughly 250mA (as measured by my multimeter at the USB port), then slowly ramps down, until at some point it drops to around 180mA and the 'Accessory not supported' error shows up.
I thought that problem might be the voltage sag, so I've tried multiple values (from 50 - 200KOhm) for the Cs resistor (R2 in my schematic), but it hasn't made a difference. I've also tried difference values (22uF - 2 x 47uF) for the Vin capacitor (C4 in my schematic). I've also tried multiple types of lithium ion battery. The one I'm currently using is rated at up to 4A, so I don't believe that's the problem. Recently I've noted that the TPS63002 chip gives off some heat during the charging and has even started to make a low volume whirring noise. Maybe the chip is damaged?
I'm including my schematic here. I'd appreciate any pointers.
Thanks!
