TPS25750: TPS25750+BQ25713 OTG shutdown

One more question, Customer wants to know how to disable PP5V power path. Could you please help answer?

Hi Dillen,

Moving all correspondence to this E2E thread and closing the other one.

Copy of other questions:

Customer test TPS25750+BQ25713 OTG(reverse charging)  function. Both TPS25750 and BQ25713 are connected with MCU. Customer find when OTG, the circuit will continue on/off. Please help support. Customer configuration process is like below:
1. initial TPS25750( related configuration has been reviewed by another E2E tickets)

2. Read type-C insert register and judge PD role : E_TPS_REG_STATUS(0X1A)

3. Based on whether the role is SINK or SOURCE, set BQ25713 OTG register and output voltage&current

4. When PD role is source, the circuit will continue on/off. Customer try to set command(get sink capabilities, send source capabilities, swap to source cap, swap to source power role). There is nothing work,  the circuit will continue on/off.

Please update with the items mentioned. Also, if possible provide schematics.

Dillen Chen said:

• Saleae scope capture of VBUS, PPHV, I2Cm data and clock (PD to BQ), I2Cs data and clock (EC to PD) with explicit 
• Block diagram of their system and JSON config for TPS25750
• EC flow chart for detecting power role, sourcing, sinking, etc. Please include details of registers, register fields, and 4CC commands used by the EC for different scenarios. 

Thanks and Regards,

Chris

Customer: How to proactively shut down the PP5V power path? Thank you.

TI: What do you mean by proactively shut down the PP5V power path? In what cases/situations would you need to do this? I do not think we have a simple control mechanism to disable/enable the PP5V path. It is controlled by the firmware during normal operation.

Thanks and Regards,

Chris

Hi Chris

We want to prohibit reverse charging in low battery or long endurance mode, so we need to achieve this by turning off the charge OTG and PP5V path.Now we can disable Charge OTG, but PP5V still provides a reverse charging path

Hi 松 石,

Need to clarify some things before we continue.

For the project/entire system:

• What power roles are supported (sink, source, drp?)
  • And at what power levels? 5,9,15V? What currents?
• Do you want ot disable the PP5V path only, or Source capability for the high voltage power path as well?
• How are you controlling the PD controller? Is there an EC/MCU in the system?
• Would disabling PD source capability and forcing the port into Sink mode work?
  • You could first clear the Process and Initiate swap to source bits in the Port Control Register (0x29)
  • Then Change the TypeC State Machine bits in Port Configuration (0x28) to Source state machine only (1h).
    • Any changes to the Port Conifg register cause a port disconnect and reconnect, so any attached devices will be disconnected, but the power role will attempt to renegotiate. If the far end device is Power Sink only, the TPS25751 port will also be configured as Power Sink so the devices will not connect and the TPS25751 will not provide a reverse charging path.

Thanks and Regards,

Chris

Hi 松 石,

I took a quick look at your schematic,

• CC capacitance is too large, the datasheet has a max capacitance of 480uF
• VUBS capacitance is too large if acting as a sink. Maximum of 10uF VBUS Cap

Thanks and Regards,

Chris

Hi Chris

We will modify the CC capacitor to 330pF according to your suggestion. Also, may I ask if there are any side effects if 1nF is used.

The cumulative capacitance of VBUS is 10.1uF. Considering the derating of capacitors under high voltage, it should be okay, right?

Hi 松 石,

The recommendation comes from the USB-C PD spec which has these requirements for CC line capacitance. I have not dealt with them myself, but I would assume the CC-line communication may run into signal integrity issues and the message may get affected.

松 石 said:

The cumulative capacitance of VBUS is 10.1uF. Considering the derating of capacitors under high voltage, it should be okay, right?

I missed the NC mark on C131. My mistake, you should be fine.

Christopher Lim1 said:

Need to clarify some things before we continue.

Let me know when you have responses to these questions, I still need to understand what you are trying to do with the PP5V path.

Thanks and Regards,

Chris

Hi Chris
For the project/entire system:
1. We are in TPS25750 Application The customization tool 7.0.4 is configured with sink and source mode
2. When PD25750 is the source, we support two types of PDO: 5V/3A and 9V/3A
3. When we stop reverse power supply, the system disables all power functions.
4. We control TPS25750 through the I2C of the MCU.
5. We force the 4CC command to switch the role to sink, but it is not successful.
6. We are using TPS25750 instead of TPS25751, and the 0x28 and 0x29 registers in TPS25750 are reserved.
7. Let me emphasize again that we are using TPS25750!!!
8. The attachment is our configuration JSON file and schematic diagramPD+charger.zip

Hi hui,

hui peng said:

2. When PD25750 is the source, we support two types of PDO: 5V/3A and 9V/3A

Did you send the correct project? The one you sent has 15V and 20V PDOs

hui peng said:

5. We force the 4CC command to switch the role to sink, but it is not successful.

What do you mean by this? The command returns a task code failure? Or you don't see it swap to Source

hui peng said:

6. We are using TPS25750 instead of TPS25751, and the 0x28 and 0x29 registers in TPS25750 are reserved.

If you do not have access to these registers as you mentioned, it is not possible to change the power functionality through register writes. The only alternative I can think of would be to make a second .json that is sink only, and load it when you want to disable source capabilities.

hui peng said:

7. Let me emphasize again that we are using TPS25750!!!

Understood, if you were using the tps25751, you would be able to use the exposed registers 0x28 and 0x29 to disable sourcing through the register writes. As mentioned in (6), the only other option is re flashing the PD controller.

This would require power cycling the device and reflashing.

Thanks and Regards,

Chris

Hi Chris:

Thank you for your reply.

2. Did you send the correct project? The one you sent has 15V and 20V PDOs

We have sent the correct project and set the PDO num to 2 according to the project requirements.

5. What do you mean by this? The command returns a task code failure? Or you don't see it swap to Source

Yes, it returned an error code to reject the task. I think it is because we have set the sink and source mode, so we cannot forcibly switch to sink or source role at this time, right?