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TPS25751: "Do not detect any legacy chargers" function

Masashi Mineda
Expert 1155 points
Part Number: TPS25751
Other Parts Discussed in Thread: BQ25792,

Tool/software:

Dear Sirs and Madams,

We are considering using a combination of TPS25751 and BQ25792.

For our application, we do not want to charge the battery when a USB Type-C connector is connected, which does not support USB PD.

So, We found the setting "Do not detect legacy chargers" in the "Enable charging detection" section.

Can We disable charging from an AC adapter connected with a USB TypeA to Type-C cable such as BC1.2 by using this function?

Does "Legacy Chargers" mean 5V/1.5A in general such as BC1.2?

We also don't want to receive power when connecting a USB Type-C adapter to a lightning connector that supports Apple Charge.

The same applies when connecting a USB Type-C connector adapter to a micro/mini USB connector.

Regards,

Masashi

  • 0
    TI__Mastermind 34256 points

    Hi Masashi-san, 

    Masashi Mineda said:

    So, We found the setting "Do not detect legacy chargers" in the "Enable charging detection" section.

    Can We disable charging from an AC adapter connected with a USB TypeA to Type-C cable such as BC1.2 by using this function?

    Charger Detect Enable [31:30] is for detecting legacy source chargers that can support BC1.2 schemes such as CDP and DCP. When this field is set to Do not detect any legacy chargers (0x0) TPS25751 will not be able to detect any BC1.2 charging schemes. This does not disable charging from a legacy source (i.e. USB-A port) when set to 0x0. 

    Masashi Mineda said:
    Does "Legacy Chargers" mean 5V/1.5A in general such as BC1.2?

    Yes that is correct, legacy chargers refer to source devices that uses the D+/D- line in the USB connector to negotiate a certain charging scheme (i.e. 5V/2.1A).

    Masashi Mineda said:
    We also don't want to receive power when connecting a USB Type-C adapter to a lightning connector that supports Apple Charge.

    Can you provide a block diagram for this scenario? For a USB Type-C to lightening cable, the USB-C side of the cable is always the source and the lightening side is the sink. Is TPS25751 the source or sink in this scenario? 

    Is there an EC/MCU in your system that can do I2C write/read to TPS25751 during run-time? 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Expert 1155 points

    Hello Lin,

    The TPS25751 used in our system performs sink(charge battery) and source(discharge battery) as DRP.

    However, when sink from an external device, we do not want to accept 5V/1.5A (USB A to C), which does not support USB PD.

    The system is equipped with an EC/MCU that reads/writes the TPS25751 via I2C.

    Regards,

    Masashi

  • 0 in reply to Masashi Mineda
    TI__Expert 8020 points

    that may not be possible when you come up in dead battery mode, unless you configure to not enable sink path unless it is 5V-3A. Please look at ADCIN settings in datasheet, how you can design resistor divider for that.

  • 0 in reply to Ghouse Mohiuddin23
    Expert 1155 points

    Hello Ghouse-san,

    I was thinking about a way to start charging only when TPS25751 becomes SINK after USP PD negotiation.

    How about using EMC to detect the "AttachedAsSink" event and enable charging of the BQ25792 only when the event is true?

    I thought about using "UFP_DFP_Event", but I couldn't find any event that indicated the USB PD connector was connected (negotiation completed).

    Regards,

    Masashi

  • 0 in reply to Masashi Mineda
    TI__Expert 8020 points

    I think, it already does that. The Charging will be disabled by default and upon PD contract the charger is programmed over I2C3.The challenge your saying is not to charge unless it is explicitly a PD contract for 5V/3A

  • 0 in reply to Ghouse Mohiuddin23
    Expert 1155 points

    Hello Ghouse,

    Please let us confirm for a few points

    I think you will choose AlwaysEnableSink for ADCIN from the options.

    Even in a dead battery state, voltage is supplied from VBUS and settings are written from EMC.

    I thought that there would be no problem if the start of charging could be determined by the GPIO's AttachedAsSink, but is it correct to understand that this is already the case in the current configuration?

    You said "it already does", do you mean that it is designed to only charge USB PD Sink?

     

    Regards,

    Masashi

  • +1 in reply to Masashi Mineda
    TI__Expert 8020 points

    I was assuming that MCU will program the part first. Even if it is dead battery it will program the Part for sinking. You should be able to log I2C3 messages and check that. GPIO AttachedAsSink will enable the part moment there is a Type-C (cc) connection. Once you have patch loaded, the programming will happen and if you have setup GPIO, it will get enabled. 

    Since you have MCU if you prevent the VBUS switch being enabled it may not power the MCU, so you are right you do need AlwaysEnableSink for ADCIN. I had mistakenly assumed that you were booting from EEPROM.

  • 0 in reply to Ghouse Mohiuddin23
    Expert 1155 points

    Hello Ghouse,

    We'll take your advice into account and give it a try.

    Thank you for your support.

    Regards,

    Masashi

  • 0 in reply to Masashi Mineda
    TI__Mastermind 37855 points

    Thanks,

    We will wait to hear back.

    Thanks and Regards,

    Chris