i am using the tps25740 from texas instruments to use a usb c port for charging a device( a laptop) and a power source for slave usb devices. since the other circuitry in the latop will not be able to handle more than 5 volts i need to configure the tps25740 to only use 5v power. from what i see, you have to leave the en9/12 pin floating. does leaving those pins floating stop the transmission of 9 or 12 (and above) volts period or just stop it initially?

all help is greatly appreciated, vesper krate


  • 1
    \$\begingroup\$ Not sure from your description, do you have a power supply that will change 5V output to 9V(12V), or not? What do you mean "to use USB-C port"? Which device has this port that you plan to use? If the consumer (your laptop) can't "handle" more than 5V but does have PD (power delivery) functionality, it doesn't matter whether you have advertising for 9/12V or not, it will receive 5V period. The TPC25740 does not "stop" transmission of 9/12V, it "turns it on" if PD negotiates so. \$\endgroup\$ Apr 21 '17 at 4:12
  • \$\begingroup\$ thank you Ali for responding, i will be more specific. the laptop will be built with a female usb type c port, attached to this port will be the tps25740. the laptop can only handle 5v power in a 2 amps max. i believe that to configure this one will need to leave en9 / en12 floating and not pulled to ground. am i reading the data sheet correctly? will the tps25740 request more power on its own, if so what do you think would be a good way to stop this function? \$\endgroup\$
    – Vesperk38
    Apr 21 '17 at 11:40

I believe the datasheet is pretty clear on this, yes, en9/12 should not be grounded to prevent advertising of higher voltages, which will be "false advertising" in your case.

However, you seem to plan to charge your laptop (to be a "consumer"), as well as provide power to slave devices when the laptop is in USB host mode (be a "provider"). This is called as "Dual-role-power" (DRP) and "Dual-role-Device" (DRD). The TPS25740 does not "request" anything, this IC is only for a "provider", it "advertises" the source capabilities. For DRP and DRD functionality you would need a different chip, which will use alternating roles, as explained here.

For details on now DRD and DRP operate, you need to examine "USB Power Delivery" specifications in addition to "USB Type-C Cable and Connector" specifications.


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