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TPS25741EVM-802: GDPG not activating with /EN12v high

Trevor Emerson
Prodigy 40 points

Part Number: TPS25741EVM-802
Other Parts Discussed in Thread: TPS25741

I have the EVM configured for 65W with a 24v supply and connected to a device that will charge with 5v and 20v profiles only.

According to the data analyser that I am using, if the /EN12v link is fitted (Don't advertise 12v) the EVM advertises 5v and 20v as expected and the connected device charges normally at 20v.

If I remove the link so that 12v is advertised, the EVM offers 5v, 12v and 20v as expected and the connected device requests 20v which is all as expected. But the EVM does not active the GDPG line to turn on the 20v to the bus even though the 20v rail has come up. So both CTL2 and 1 have gone low. Also, because GDPG does not turn on the 20v to the bus, the TPS25741 does not send the PS_RDY message to the device which causes the device to send a hard reset to the EVM. This scenario now cycles indefinitely.

Any idea why GPDG would not activate the FET when 12v is enabled but not being requested.

Help please

Trevor Emerson

  • 0
    TI__Guru 50120 points

    Hi Trevor,

    Can you provide a scopeshot of the following testpoints for debugging?

    • TP8(GDPG) 
    • TP16(VBUS)
    • TP5/6 (CTL1, CTL2)

    When CTL2 and CLT1 states are low, the voltage contained in PDO requested by UFP is 20V which should coincide with your setup since your device only accepts 5V and 20V (8.3.10 in datasheet). 

    The expected operation of the TPS25741 is that during a 5V contract, the G5V gate driver is turned on. To source a voltage higher than 5V, the G5V gate driver is disabled and GDPG gate driver is enabled. 

    Regards,

    Jimmy Hua 

  • 0 in reply to Jimmy Hua
    TI__Guru 50120 points

    Hi Trevor,

    The TPS25741EVM is lay out to only be able to output 2 different voltages. Even though you see there are 3 different PDO(5V,12V,20V), the EVM only enables 2 voltages because the board is set up as Power mux implementation shown below. 

    It should be noted that the TPS25741 IC allows three different voltage advertisement if you plan on using the DC-DC implementation.

    Regards,

    Jimmy Hua

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