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TPS65987EVM: Interfacing with a TPS65981 chip (TPS65987EVM source, TPS65981 sink)

Dylan Johnson
Prodigy 20 points

Part Number: TPS65987EVM

Hello,

I'm attempting to use the TPS65987EVM to supply 20V to a custom PCB that uses a TPS65981 for USB power delivery. I'm using the TPS65987EVM for USB-C Alternate Mode DisplayPort as well as 20V/3A power delivery, but I'm only experiencing an issue related to power delivery at the moment. I originally used a TPS65986EVM to source 20V to the same custom PCB with the TPS65981. As the TPS65986 is obsolete, we've been looking into getting the TPS65987EVM as a bridge for testing DisplayPort over USB-C with 20V/3A power delivery instead. At the moment I'm testing without a display, so the PCB is drawing ~60 mA when power is established.

I've loaded what I hope to be the appropriate settings to the TPS65987EVM for my application (attached below, along with the original TPS65981 settings). When attempting to connect the custom PCB with the TPS65987EVM, the VBUS LED on the TPS65987EVM appears to be flashing every second. Taking a look at VBUS, it's alternating between 0 V and 5 V every second. CC1 appears to have the same behavior of voltage shifting between 0 V and 5 V, while CC2 is at a steady 1.7 V. LEDs D14 and D15 are illuminated when connecting the cable. D19 and D20 are illuminated when connecting the barrel jack, with no change after connecting the USB-C cable. Flipping the cable or swapping the USB C-to-C 3.1 cable out for another one doesn't appear to help.

Looking at the debug registers:

Status -

  • Plug is present
  • Connection is present, Ra detected or Rp detected with previous Ra detection
  • Plug orientation is upside-down
  • PD Controller is Source
  • PD Controller is DFP
  • VBUS Status alternates between vSafe0V and vSafe5V
  • No high or low voltage warnings

Power Path Status -

  • PP1_Cableswitch CC1 enabled (system output)
  • PP2switch enabled (system output)
  • PP1_CABLE Enable is set
  • All above status resisters are disabled with VBUS is at 0V

Number of Source PDOs are apparently at 0 at all times, though Active Contract PDO will show 20V/3A active contract when VBUS goes to 5V.

Note that the TPS65981 was programmed with the 6.1.1 TPS6598x Application Customization Tool GUI, while the TPS65987EVM was programmed with the TPS6598x Application Customization Tool 6.1.2 GUI. Let me know if any other information is needed.

TPS65981-Config.pjtTPS65987DDH_EVM_DFP_5_20_Source.pjt

--Dylan Johnson