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TPS2540A DCP & CDP device support

Other Parts Discussed in Thread: TPS2540A, TPS2540, TPS2546

I'm using the TPS2540A in a charging application for a Type A USB port where there's also a Type C port that can connect to a laptop.  The devices needing charged could be any laptop, phone, tablet, etc that can charge from a USB Type A port.

There are two possible configurations for the TPS2540A that make sense: DCP (dedicated charger port) with auto-detect or CDP (charging downstream port).  Our plan was to use CDP mode whenever the Type C is connected to a laptop to allow data connection between the laptop and the device plugged into the Type A port, otherwise use DCP mode.  However, I'm uncertain about device compatibility in these two modes.  It appears DCP auto-detect mode has more options than CDP mode, and thus would be able to charge more devices at the higher current.  

Below are some questions that would help guide me to the ideal setting, relying on TI's experience with device compatibility and the various charge handshaking methods:

1) CDP mode supports BC1.2, and DCP supports BC1.2 DCP and divider mode.  Is it a true statement that DCP will support maximum charging to more devices?

2) If switching from DCP to CDP mode on the TPS2540A with a device connected and possibly charging, will it properly renegotiate to use the maximum charging power for that mode?  What about CDP to DCP mode?

3) Is the TPS2540A responsible for the CDP power negotiation or the host side USB port?  What is the implication of staying in CDP mode when there's not a USB data connection to a host USB port?

Thanks,

Scott

  • Hi Scott,


    This device falls under the Power Interface forum.  I will go ahead and move this post.


    Thanks,

    Alek Kaknevicius

  • For new designs, I would recommend TPS2546 over TPS2540. TPS2546 will support many more portable devices.

    The charge mode chosen really depends on your end product and if you will need to fast charge while transmitting USB 2.0 data. A host controller is responsible for changing the TPS2546 mode via the CTL pins. There is a diagram in the TPS2546 DS on page 28 (Figure 38) to help understanding the charging states and modes. This datasheet will also have much more information on the operation of each mode including DCP auto mode which can automatically detect/change based on what is detected on the charging port (see Figure 37.