• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 377 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TPS2546: Mode Selection inquiry

Kelvin Tee
Genius 10035 points
Part Number: TPS2546
Other Parts Discussed in Thread: TPS2549

Hi Emma

I have few questions to ask about TPS2546 configurations.

Below is the application scenario on the USB port

#1. Supports USB thumb driver and HDD for data transfer
#2. Supports various mobile phones for charging only mode. No data is required

Questions

1. Does below mode best suit for the applications such as

SDP/CDP Auto Switch for #1 
DCP auto for #2

2. If only configure SDP/CDP Auto Switch for #2.  What happened to the phone’s charging condition? Would it work similar as DCP auto?

3. Since there is no SDP/CDP - DCP Auto switch mode, user has to perform software setting that depends on what portable USB device is inserted. Is there any detection that could assist to inform MCU to decide which mode to configure? Eg. When thumb drive / HDD is connected, it selects SDP/CDP and if a phone is connected, it switch to CDP Auto.

4. Do you have the phone compatible list supported by this device with DCP auto?

5. Do you have the feature comparison of TPS2546 vs TPS2549 ? Cable compensation is not required here. Does it make sense to use newer TPS2549?

Rgds
Kelvin

  • 0
    TI__Genius 9630 points

    Hello Kelvin, 

    1. a) The CDP/SDP auto switch is used for non BC1.2 compliant devices that enumerate only as SDP or DCP (not CDP). These phones as they fail to establish data connection in CDP mode but rather see a CDP port as a DCP port and do not exchange data. The CDP/SDP auto switch corrects this problem, as explained by the datasheet, pasted below. If you predict that these non compliant devices will be used, then this mode may be preferable.

     

    b. For mobile phone charging DCP auto will work.

     

    2. The phone will do one of two things:

      1. If the phone wrongly classifies the CDP port as a DCP port, VBUS will discharge, and the port will switch to SDP in order to establish a data connection. The port will switch back to CDP but the phone will stay in SDP charging.
      2. If the phone correctly identifies CDP, it will charge in CDP.      

     

    3. The MCU dictates setting depending power state the system is in. The TPS2546 does not offer any output that indicates what type of device is connected. The TPS2546 is designed to respond to system dictating what state the part should be in. If the device is in CDP/SDP, charging will still occur. However, you will not get the non-compliant charging modes (divider 1 and divider 2) offered by DCP auto. 

    5. There are a few differences between the chips, and you preferred characteristics will determine which will work best for you.

    - The TPS2549 can compensate for a voltage drop in long cables and keep the remote USB port output voltage constant where as the TPS2546 is not designed for long cable compensation.

    - The TPS2546 has a larger configuration of modes that it can accommodate, which is shown in each device's truth table.  The TPS2549 only offers DCP auto and does not allow access to individual DCP modes that the 46 offers. The TPS2549 also offers divider 3, TPS2546 offers only divider 1 and 2.

    - The TPS2546 has also the load detect power wake functionality. 

    Thanks,

    Emma

  • 0 in reply to Emma Hoying
    TI__Genius 10035 points

    Hi Emma

    Thanks for the answer.

    1. Back to earlier question, is there a single configuration that supports below application?
    - Supports USB thumb driver and HDD for data transfer
    - Supports various mobile phones for charging only mode. No data is required

    2. If choose SDP/CDP auto for media (thumb drive/hdd) and DCP auto (for phone charging only)
    Customer idea is when the equipment is turn on condition, the MCU set TPS2546 as SDP/CDP auto and when equipment is in standby mode, it turns into DCP auto.

    During the transition of SDP/CDP to DCP or reciprocal (equipment turn on <--> standby) while a phone is remain inserted, is there any problem ?
    What is the proper procedure to perform the configuration mode change ?

    Rgds
    Kelvin

  • 0 in reply to Kelvin Tee
    TI__Genius 9630 points

    Hello Kelvin,

    1. Yes, CDP (1111) will support the thumb drive, HDD for data transfer, and charging of phones. 

    2. This is a typical use case of the port. If the phone is transferring data, there could be a potential corruption if the mode switches from CDP or SDP2 to DCP_auto. When this mode change occurs, VBUS will discharge which will disconnect the DP/DM lines. If you want to ensure that there is no VBUS discharge, you can switch from CDP to SDP2. This will ensure that the data lines are not disconnected. If the phone is not transferring data, there will be no issue switching from CDP or SDP2 to DCP_auto. VBUS will discharge, the phone will enumerate again, and the phone will begin charging from DCP_auto. 

    The procedure to change modes involves changing the CTL pins. The CTL pin changes and corresponding states can be seen in the truth table from the datasheet:

    Thanks,

    Emma

  • 0 in reply to Kelvin Tee
    TI__Genius 9630 points

    Hello Kelvin,

    1. Yes, CDP (1111) will support the thumb drive, HDD for data transfer, and charging of phones. 

    2. This is a typical use case of the port. If the phone is transferring data, there could be a potential corruption if the mode switches from CDP or SDP2 to DCP_auto. When this mode change occurs, VBUS will discharge which will disconnect the DP/DM lines. If you want to ensure that there is no VBUS discharge, you can switch from CDP to SDP2. This will ensure that the data lines are not disconnected. If the phone is not transferring data, there will be no issue switching from CDP or SDP2 to DCP_auto. VBUS will discharge, the phone will enumerate again, and the phone will begin charging from DCP_auto. 

    The procedure to change modes involves changing the CTL pins. The CTL pin changes and corresponding states can be seen in the truth table from the datasheet:

    Thanks,

    Emma