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Original question:

TPS2540EVM-623: CDP Mode

TPS2540: CDP mode support

Sathish Kumar
Prodigy 40 points
Part Number: TPS2540

We are looking at using TPS2540 in our project. Our use case scenario is

1) USB host where our product will be plugged into only supports CDP charging

2) Integrated circuits used in our product will be USB device and only supports SDP charging profile

If we configure the CTL1,2 & 3 bits to high(for CDP BC1.2) in TPS2540 and place in between USB host and our product, will this solve our problem in charging?

  • 0
    TI__Mastermind 28830 points

    Hi Sathish,

    There should not be an issue here to begin with. SDP devices can charge with a CDP charger and CDP devices can charge with an SDP charger. The type of charger and device do not have to match up in order for charging to occur. The two combinations I just mentioned will still charge but default to a charging of 5V 0.9A. The benefit for BC1.2 comes when a CDP device is connected to a CDP charger. In such a scenario, the device will sink 5V 1.5A. But once again, this combination is not mandatory.

    Let me know if this helps answer your question

  • 0 in reply to Adam Mc Gaffin
    Prodigy 40 points

    Hi Adam,

    Thanks for your feedback. May be i didn't explain the situation correctly. In our project, during normal operation we can draw 5V,0.5A from the host.

    But when the hosts goes to sleep/Rest mode, it only supports charging through CDP.  But we enumerate as SDP, so it stops power to our device when it enter sleep/rest mode. This is where can we use TPS2540 in between host & device, so during normal operation + Sleep/Rest, host always thinks we are CDP device  

  • 0 in reply to Sathish Kumar
    TI__Mastermind 28830 points

    Hi Sathish,

    I do not believe the TPS2540 would work in this situation. I still do not believe there is a problem here that needs to be fixed with hardware. 

    How BC1.2 works is that the device needs to determine what type of charger it is connected to. So the "advertisement" really comes from the charger and not the device. You cannot have both a device and charger advertise charging modes. 5V is always present on VBUS with BC1.2, so the purpose of the negotiate is for the device to figure out the data and power capabilities of the charger it is connected to. CDP and DCP both allow up to 1.5A of charging and SDP allows up to 900mA of charging. Both CDP and SDP allow data transfer and DCP does not.

    So if your system only needs 500mA, once your device detects that it is connected to a CDP charger, your device should take this as the charger can support 1.5A and is capable of handling data.

  • 0 in reply to Adam Mc Gaffin
    Prodigy 40 points

    Hi Adam,

    Thanks for the reply. This clears up everything.