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Charging current at TPS2543

masa0301
Intellectual 960 points
Other Parts Discussed in Thread: TPS2543, TPS2540, TPS2511

Hi

Please tell me that charging current connecting at TPS2543 and IPAD2.

Connecting conditions are as follow.

1,Connect the IPAD2 and TPS2543EVM,Vbus in shorted by external jumperwire, and opend the Vout of the EVM.

   Charging current is 1A...Divider1

2,Condition of nomal use

   Charging current is 1.6A...Divider2

My question is below

Q1,Why current value what is the difference 1 and 2

Q2,Why is it divider1 case of 1

Q3,Why no matter how flows only 1.6A case of 2(I think usualy 2.1A....)

Q4,Please tell me the condition that can change current 2.1A at TPS2543EVM and IPAD2

Best regards,

masa

  • 0
    TI__Mastermind 42795 points

    The charging current is controlled by the load plugged into the output of the TPS2543 unless that charging current exceeds the mode set by TPS2543 ILIMx pins. TPS2543 has modes where it can sense a load current and then switch switch modes (divider 1 to divider 2 for example), but it is up to the load to determine how much current it should consume.

  • 0 in reply to Eric Wright
    Intellectual 960 points

    Eric-san

    Thank you for your reply.

    I am sorry that it seems our previous explanation was not enough.

    So let us add the following matters.

    4666.case1 and case2.pptx

    Q5,Why case1 and case2 not same divider mode

        The Case2 can not use divider2? (When use  the TPS2511EVM, we can use divider2...)

    Best regards.

    masa

     

  • 0 in reply to masa0301
    TI__Mastermind 42795 points

    Hi Masa-san,

    Before the IPAD, divider 1 was enough current for IPOD and Iphone. Then came IPAD and the D+/D- voltages reversed and required divider 2. So, TPS2540 could not fast charge IPAD unless D+/D- wires were crossed but TPS2543 can do this automatically using "DCP Divider Charging Scheme" and "DCP Auto Mode" described on pg 17, 18 of the TPS2543 datasheet.

    For TPS2511, since it is dedicated for either a 5W or 10W charger, D+/D- should be connected according to figures 35-38 (note the D+/D- connection for 5W or 10W applications).

    Also keep in mind that the power switch in these devices has a programmable current limit which passes all current up to the set point and then limits higher currents by reducing OUT voltage (foldback or current limit). The device being charged regulates current up to the current limit set by the TPS254x (or TPS251x) power switch current limit. The charging device can also reduce it's demand current based on the VBUS voltage at the device connector (voltage drop between power switch and charging load) and this might explain why the IPAD is only demanding 1.6A. That is why TPS2511 has the  cable compensation feature.

    Regards, Eric