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TPS2549 in DCP mode, if remove the load, then attach a new USB device, how to communicate with USB host(in MCU side)

zhimin xia
Prodigy 230 points
Other Parts Discussed in Thread: TPS2549

I have 1 question about the application of TPS2549

if need charge iPAD, it need 2.4A charge current, we need set TPS2549 in DCP mode, in this stage, if plug out the iPAD from USB port, Can TPS2549 detect the action and indicate it to USB host(in MCU side)?

if can not, that means, TPS2549 is still in DCP mode, the D+/D- is disconnected with DP/DM, in this time if attach another USB device(like U disk), how let MCU know there is a new USB device attached? and change the TPS2549 from DCP mode to SDP/CDP mode?

  • 0
    TI__Mastermind 42795 points
    You may be able to monitor the STATUS pin which is active in DCP (001) and CDP (111) modes to know if there is a load drawing current above the load detection threshold.
  • 0 in reply to Eric Wright
    Prodigy 230 points
    Dear Eric
    Thank you.
    In above examples, if iPAD complete charge, the Statues will be de-asserts, in this time, if I remove the iPAD, statues will not change, after that, when I attach a U disk, because it is a Mss storage device, there is no any charge current, so Statues pin will keep in "1" level. it may not work.
    I think the key point the how to know one device is removed or attached in DCP mode, if we can detect, we can set the TPS2549 to CDP, then host know the device is removed or 1 device is attached.
    by the way, In datasheet said as below, the load detection is by ILIM_low, in 001 and 111 mode, we can set ILIM_Low to detect the charge or not, is it correct?

    STATUS asserts in a charging port when the load current is above ILIM_LO + 40 mA for 210 ms (typical).
    STATUS de-asserts in a charging-port when the load current is below ILIM_LO – 10 mA for 3 seconds (typical).
  • 0 in reply to zhimin xia
    TI__Mastermind 42795 points
    You can always test out each scenario using the EVM and see if it will meet your needs.