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TPS2511: Issues with IOS devices

Ross Hymel
Prodigy 100 points
Part Number: TPS2511

I designed a simple USB pass through device utilizing the TPS2511 that allows me to control the current draw of a connected device while it is charging. It works fine for Android devices, but when I try it with Apple device (iPhone/iPad) and set the current limit above 100 mA, I get the following warning:

"This accessory may not be supported"

The Apple device then limits the current draw to 100 mA no matter what value I set the ILIM_SET resistor to. I've attached a schematic of the design. Anyone have any ideas what is going on? Could it be related to the ESD protection devices?USB_Charger.pdf

  • 0
    TI__Mastermind 42795 points

    What is the current capacity of the VBUS source at P1? It should be higher than what the TPS2511 current limit is set to. You could put a scope on P1-1 and see what happens when the Divider mode device is attached at J1.

  • 0 in reply to Eric Wright
    Prodigy 100 points
    The current capacity is whatever I plug it into, which is usually a dedicated charger with much higher capacity. I tried it with the charger that comes with my iPhone, which I believe is 1A, and still no luck. I will try with a scope tomorrow and report back.
  • 0 in reply to Ross Hymel
    Prodigy 100 points

    I attached a scope to P1-1 and observed that no voltage droop occurrs when a device of any flavor is attached at J1. However, significant droop occurs at the OUT pin (8) of the TPS2511. IOS devices seem to sense this droop and discontinue higher current charging, as the voltage at pin 8 restores to 5.0V rather quickly. Android devices don't seem to care about the droop and continue charging happily with decreased VBUS. Any ideas why the voltage droops? I am going to dtry lifting pin 8 and directly connecting P1-1 to J1-1.

    Some screenshots, upper blue line is J1-1 (U1-8), teal line is J1-2:

    Android plug-in:

    IOS plug-in:

    Screencaps of D- on plugin:

    Android:

    IOS: