TUSB321: CC logic controller as a SNK(UFP)

Hi Martin,

Martin Likavec said:

1. CURRENT_MODE - left it floated or? Because this pin is use only for DFP or DRP mode. I didn't find any information in datasheet how to connect this pin, when PORT = LOW (UFP).

You can leave the pin floating, there should be no issues there.

Martin Likavec said:

3. VBUS_DET - connected through resistor to the load switch output

What is enabling the load switch? It looks like the EN pin of the switch is connected to the OUT pins of the TUSB321. If the TUSB321 does not see VBUS on the VBUS_DET pin, then it will not be able to detect whether a DFP is connected or not. It's better to route VBUS to VBUS_DET so that it will see VBUS once anything is connected. If the TUSB321 does not see a connection, both the OUT pins will be high, per table 2:

Martin Likavec said:

4. ID - this pin is not active in sink(UFP), right? So, I need to control the load switch different way. I want to use OUT1/OU2 pins

Yes, ID can be floating.

Martin Likavec said:

5.  OUT1/OU2 - these pins report the source current capability, right? If the high current source (3A) will be connected, then both OUTx pins will be LOW (Table 2). So, I want to connect both OUTx pins to OR gate inputs and when both OR inputs will be LOW, then OR output will be LOW and turn ON the VBUS load switch.

VBUS is required for the TUSB321 to see a USB-C connection. If VBUS is not enabled for VBUS_DET, then it will not be able to detect a connection. Additionally, OUT1/OUT2 are meant to communicate to your device typically the amount of power that can be drawn, based on what the host is advertising. 

Martin Likavec said:

Please, check if my circuit is correct.

Just to confirm, is the DIR pin being used to control a mux based on the FLIP orientation of the type-C cable?

Is your intention with the load switch to not allow VBUS to be connected unless connected to a 5V/3A DFP?

Thanks,

Ryan

Hi Ryan,

Ryan Kitto said:

What is enabling the load switch? It looks like the EN pin of the switch is connected to the OUT pins of the TUSB321.

I want to enable the load switch when only 5V/3A source will be connected. So, I got idea to use OUT1/OUT2 pins. Because, TUSB321 don't provide any other solution how to control load switch in UFP mode.

Ryan Kitto said:

If the TUSB321 does not see VBUS on the VBUS_DET pin, then it will not be able to detect whether a DFP is connected or not. It's better to route VBUS to VBUS_DET so that it will see VBUS once anything is connected.

Fine, I understand and I will connect VBUT_DET on the load switch input side (5VBUS).

Ryan Kitto said:

If the TUSB321 does not see a connection, both the OUT pins will be high, per table 2

Yes, this correct. Then the OR gate output will be high and load switch will be OFF.

Ryan Kitto said:

Additionally, OUT1/OUT2 are meant to communicate to your device typically the amount of power that can be drawn, based on what the host is advertising. 

Yes, this was my idea. When OUT1/OUT2 report that 3A source is connected, then I will turn ON the load switch according to OUT1/OUT2 signal and OR gate.

Ryan Kitto said:

Just to confirm, is the DIR pin being used to control a mux based on the FLIP orientation of the type-C cable?

No, my device don't have data capability. So, I don't need the DIR pin.

Ryan Kitto said:

Is your intention with the load switch to not allow VBUS to be connected unless connected to a 5V/3A DFP?

Yes, you are right. I want to accept only 5V/3A DFP. Because, the device power consumption is 2A.

Thank you for your help. If you have any other comments, let me know.

Best regards,
Martin

Hi Martin,

Martin Likavec said:

Yes, this was my idea. When OUT1/OUT2 report that 3A source is connected, then I will turn ON the load switch according to OUT1/OUT2 signal and OR gate.

Are these reporting to the device that 3A is possible? If not, is the device only possible of pulling 2A? It cannot pull a lower amount of power?

Martin Likavec said:

Fine, I understand and I will connect VBUT_DET on the load switch input side (5VBUS).

That should help with detecting VBUS, yes.

I will say that this isn't an application we typically see with this device, however, as long as there is proper communication over the CC lines and VBUS is properly routed, I don't see why it wouldn't work. I don't have any other comments.

Thanks,

Ryan

Hi Ryan,

Ryan Kitto said:

Are these reporting to the device that 3A is possible? If not, is the device only possible of pulling 2A? It cannot pull a lower amount of power?

I will tell you more about my device, why I need to check someway, if enough powerful Source is connected.

This device is something like multi-charger or dock (4 slots) for another devices which each take around 500mA during the charging internal batteries. 

I need to guarantee that the charging dock will always works without problems. Because if there was no control/check whether a sufficient power source is connected, it would happen that out of four connected devices, only one or two would be charged at full power, etc.
Because it could happen that someone connects the charging dock to a low current charging port like 0.5A-1A and then the charging will not work properly with 4 devices in the charging dock.

That's why I decided to check it so that a 5V/3A source must be connected, since a 5V/2A source cannot be checked in any way.
.
This solution has come to my mind as the only one, that only in this case I can guarantee, that the charging dock will always run at full power.

Let me know, if you have any idea.

Thanks
Martin

Hi Martin,

Okay, got it. I'm not sure this application will actually help your system pull 5V3A however. For the Type-C spec, if a Source advertises additional current, such as 1.5A or 3A, then a sink downstream can take advantage of this, and must adjust the amount of current consumed within tSinkAdj listed in the Type-C spec:

However, if there is no sink that is actively being told how much current can be consumed, then it may not consume the amount of current it needs. Additionally, it needs to set the amount of current consumed within the time tSinkAdj, so it would not be able to change the amount of current being pulled whenever it needs more or less.

Is there a Sink in your system that will actively pull the amount of current it needs at all times? Or is the amount of current your system will use intended to fluctuate based on the number of ports in use?

Section 4.6.2 of the type-C spec has more info on how VBUS is provided over a type-c cable if you want to know more.

Thanks,

Ryan

Hi Ryan, 

Ryan Kitto said:

Okay, got it. I'm not sure this application will actually help your system pull 5V3A however. For the Type-C spec, if a Source advertises additional current, such as 1.5A or 3A, then a sink downstream can take advantage of this, and must adjust the amount of current consumed within tSinkAdj listed in the Type-C spec:

I am not sure if we understand each other correctly.

Do you mean with above statement, that I wanted to take constant 5V/3A? No, I don't. I want to only have the 2-3A available. 

I'll explain how the charging works.

As I mentioned, each device connected to the dock takes a maximum of 500mA during charging.

500mA is not a constant current during the entire charging period. The Lipo battery in device is charged according to a set curve. So the more charged the battery is (more %), the charging current decreases.

So the maximum current 500mA*4=2A will be taken from by the dock only for a certain time, as long as the batteries of the four connected devices have a low SOC (low % charge).

Just for information... PMIC which we use for lipo batteries in connected devices is BQ25896

Regards, 

Martin

Hi Ryan,

Thank you very much for information and confirming my application.

Otherwise, it doesn't matter, that we didn't understand each other right away.

Regards,
Martin