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TPS25740: Is it ok operating with a sink attached but no charging supply provided?

Marek Roszko
Intellectual 380 points
Part Number: TPS25740
Other Parts Discussed in Thread: LM5175, TPS2540

So I have a TPS25740 and a DC-Dc converter, the LM5175.

The DVDD of the type-c controller is attached to the enable of the converter. When the sink is attached, DVDD goes high and the controller is enabled.

I have the converted enable also ANDed with a second signal for the enable. It can happen that the DVDD goes high but the second signal is low.

Is the type-c controller ok having the sink attached but no charge power coming through? The controller is powered from a separate power source than the converter.

  • 0
    TI__Guru 50120 points

    Hi Marek,

    I'll take a look into it and get back to you since I've never seen an application where a sink is attached but no pdo contract has been made.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Intellectual 380 points
    Yea in this application, I want to keep the buck-boost disabled to conserve power as the supply is a battery pack. Depending on the battery pack attached I want to either allow or disallow use. I could use the gate disable on the type-c controller but the user may leave the device attached which would incur losses as the buck would be running :/
  • 0 in reply to Marek Roszko
    TI__Guru 50120 points
    Hi Marek,

    As a part of the TPS25740 device design, there will always need to be a PDO advertised if a sink is attached. The device is designed such that when a sink is attached and detected, VBUS turns on and the necesary current is advertised depending on PD or non-PD sinks. There is also a safety feature where if the voltage on the CC lines exceeds the detach threshold then the VBUS lines are removed and the device begins watching for a sink attachment again.

    Regards,
    Jimmy
  • 0 in reply to Jimmy Hua
    Intellectual 380 points
    I'm asking if the TPS2540 attempts to turn on the VBUS but can't because the DC-DC converter is being held off by a second signal, is it ok staying in that state or will it cause damage?
  • 0 in reply to Marek Roszko
    TI__Guru 50120 points
    Hi Marek,

    I can't say for certain since most of the application using the TPS25740 have a power supply system connected to the USB port controller in a single power path topology. With that said, I don't think the IC would be damaged.

    Can you help me understand what application this will be used for? Sounds like some type of power saving circuit where you would enable/disable the dc-dc converter to reduce power consumption.

    Regards,
    Jimmy
  • 0 in reply to Jimmy Hua
    Intellectual 380 points
    >Can you help me understand what application this will be used for? Sounds like some type of power saving circuit where you would enable/disable the dc-dc converter to reduce power consumption.


    Yes, the application is in combination with a battery pack. There are multiple variants of the battery pack and only ones that we manufacture are to be supported by the device. The user can still put the device on other batteries however ideally we don't waste too much power discharging the battery if not in use.