This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2549: Not seeing more than 1.5A charging using TPS2549Q1EVM-729 eval board

Part Number: TPS2549

Using the eval board, I have charged several different Apple devices but I not recorded more than 1.5A charging current.  The devices are iPhone 12 Max, iPhone Xs, iPhone 6s Plus, Ipad pro (9.6" old model), and iPad 8th gen.

I powered the eval board (one power method at a time) from the 7-18V input (at 9V) and without the on-board DC/DC by powering with +5V on J4-2 and GND on J6-2.  The CTL3-1 signals are set for DCR HI.  ILMI_HI resistor is 19.1k-ohms.

My DC supply indicates approximately 1.5A charging for both power input types - math is required to estimate 1.5A output with the 9V input.  If I add an ammeter inline with the USB cable, the charge current drops to 1A.  The 1A current is observable by the DC supply current monitor also.  Long, lossy cables also result in 1A charging, as reported by the DC supply - no inline ammeter for this measurement.  I observe that slightly increasing the voltage causes the current to approach 1.5A.  The D+/D- pins each measure 2.7V to GND, so it appears that the divider3 circuit is active and always on.

Should I be able to achieve > 1.5A charging current on Apple devices when using TSP2549 (Q1 or non-Q1)?  Note that the eval board uses TPS2549Q1RTE rather than TPS2549RTER/T.  I assume the "Q1" part is equivalent functionally to the non-automotive part, but I do not see any data at the website about the "Q1" part.

  • I'm not sure why the Q1 datasheet didn't show up earlier, but I do see it now.

  • Hello,

    Yes you should be able to achieve > 1.5A, however from what you described it sounds like you are in CDP mode, not DCP mode. DCP mode is the only mode capable of > 1.5A of charging. CDP's charging limit is 1.5A. Please try one of the DCP configurations and let me know your results.

    Please keep in mind that it is up to the sink to determine how much current to pull, so current draw will also depend on the sink.



  • The part is configured for DCP HI mode.  CTL1-3 = 001.  I misspelled DCP as DCR in my original message.

  • Since it is up to the sink to determine how much current to draw, is there a way to force an apple device to pull more than 1.5A curing charge? 

    I assumed that simply advertising the charger capability with divider3 (2.7V on D+ and D-) would cause the devices to charge at 2.4A.  I created a test with a cable with +5V on power and a resistor divider set to 2.7V on D+ and D- and I also observe 1.5A charging.  I see 2A charging if the voltage is increased to around 5.2V (measured at supply output and not phone input).  As I increase the voltage more, the charge drops back to 1.5A.

    Is there a strict voltage requirement at the phone input that must be maintained to achieve 2.4A charging?

  • Hi Phillip,

    Not that I am aware of, but that would probably be a better question for the company that makes the sink devices you are testing with. 

    You should check the power supply if changing the voltage changed the charging. You could be maxing out the current the power supply is outputting if your voltage is too low.