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Dual STUSB4710 Power Management

YunusBasegmez
Associate II

I am designing a usb type-c charger. 

I want to use 2 microcontroller and 2 STUSB4710.

Type-C Output will be 20V 3.35A 67W.

I want to do power management between these USB Type-C outputs.

I have questions. Can you please answer them?

 

1. Are there any I2C command to close the output pmosfets with STUSB4710?

2. Can microcontroller reduce the output current capabilities of STUSB4710 while a device connected to USB Type-C sinking some current. For example,

  • Default output contract is 20V 2.25A
  • Send I2C command to STUSB4710 and change the output capabilities to 20V 3A.
  • Output contract is now 20V 3A.
  • Attach a usb device which sinking 20V 3A power and start consume 60W.
  • Send I2C command to STUSB4710 and change the output capabilities to 9V 2.25A.
  • STUSB4710 send message over CC communications.
  • Sink device reduce power consumption to 9V 2.25A.
  • Is the scenario possible? If there is a problem, can you correct it?

3. Is there any other way to reduce sinking current of the connected usb device?

4. STUSB4710 supports 20V 5A. But Vconn is not supported with STUSB4710. Is there a standard incompatibility?

5. Is 20V 3.35A type-C output possible with STUSB4710?

6. I have found this post https://community.st.com/t5/interface-and-connectivity-ics/stusb4700-4710-i2c-register-details/td-p/234334. But I did not find any clear guidelines(step by step) for changing register and effects of it. Also some registers contained TBD values.

10 REPLIES 10
NBALL
ST Employee

Hello
AS per USB power delivery, source cannot provide only 20V/3A.

All power sources need to follow so called 'power rules': 67W charger needs to at least propose: 5V/3A - 9V/3A - 15V/3A and 20V/3.35A
Current can be higher than 3A for PDO< 20V but it needs to be always <=67W if the charger is labelled 67W

To provide current >3A, source shall ensure that the cable can sustain more than 3A. All USB cable are guarantee to sustain 3A but not all of them can sustain 5A. In order to read cable characteristics, source shall supply Vconn and shall send messages dedicated to cable (SOP' messages).
STUSB4710 cannot do this functionality. To propose more than 3A with stusb4710, the source needs to be so called 'captive cable': i. e cable is undetachable. connector is a plug instead of being a receptacle.

I port is labelled 67W max, overall power can be reduced due to sharing but voltage nodes should be kept, as per USBPD spec. i.e if power is reduced to 40W, it should offer 5V/3A - 9V/3A - 15V/2.66A - 20V/2A

Hope it helps

Best regards

Nathalie

YunusBasegmez
Associate II

Thanks you for information. But I did not see answers of questions below. Can you please reconsider it?

1. Are there any I2C command to close the output pmosfets with STUSB4710(or STUSB4761)?

2. Can microcontroller reduce the output current capabilities of STUSB4710(or STUSB4761) while a usb sink device connected to USB Type-C sinking some current. For example,

  • Default output contract is 20V 2.25A
  • Send I2C command to STUSB4710(or STUSB4761) and change the output capabilities to 20V 3A.
  • Output contract is now 20V 3A.
  • Attach a usb device which sinking 20V 3A power and start consume 60W.
  • Send I2C command to STUSB4710(or STUSB4761) and change the output capabilities to 9V 2.25A.
  • STUSB4710(or STUSB4761) send message over CC communications.
  • Sink device reduce power consumption to 9V 2.25A.
  • Is the scenario possible? If there is a problem, can you correct it?

3. Can microcontroller reduce the output current capabilities of STUSB4710(or STUSB4761) while a usb sink device not connected to USB Type-C. For example,

  • Default output capabilities of STUSB4710(or STUSB4761) is 20V 2.25A.
  • Send I2C command to STUSB4710(or STUSB4761) and change the output capabilities to 20V 3A.
  • Output capabilities is now 20V 3A.
  • Send I2C command to STUSB4710(or STUSB4761) and change the output capabilities to 9V 2.25A.
  • Is the scenario possible? If there is a problem, can you correct it?

4. Is there any other way to reduce sinking current of the connected usb device?

NBALL
ST Employee

Dear  YunusBasegmez,

Question1:

There is no possibility to close power mosfet thru I2C command: it is only managed by hardware.

Question 2:

If you need to send some updated source_cap, you need to:

1/ update the PDO fields into PDO registers
2/ write @x1A = x02 : this command will send source_cap message with PDO stored into registers

Please note that stusb4710 does not limit the current. It sends instruction to sink about the max current available. Sink is responsible to not sink more than the request done.

question 3:
Updating the current in source_cap to force sink to reduce its power is the only way to reduce the sinking current

question4: 

STUSB4710 can support 100W only in case of captive cable application. In this case, there is no need to send message to cable to know if it can support more than 3A

Question 5:

More than 3A is not allowed by the standard if source does not check that cable can sustain more than 3A

I hope that it will help 🙂

Best regards

Nathalie

  

Thanks you for a quick respond.

What can you say about STUSB4761?

Can STUSB4761 handle this scenarios?

Can you answer the same questions for STUSB4761?

Situation on STUSB4716 is unpleasant.

No register description available and without a doubt different to 4700A.
You have to use STSW-STUSB005 tool to create and export a NVM configuration but you never know which bit does what.

First PDO Profile is always 5V and without cable ID chip STUSB4761 will not deliver more than 3A.
You can outsmart it with a wrong current shunt but I dont know if a 5A negotiation ist possible without a 5A cable ID chip.

You can't control mosfets directly over I²C but you can manipulate the temperature measuremen.

Look at page 7 in Datasheet.

 

Hello

There is no possibility to handle same scenario using stusb4761.

Only way to send new src_cap with stusb4761 is to use Tsense: depending on voltage, stusb4761 will act as if temperature has changed and will resend src_cap with different current on its PDOs.

Best regards

Nathalie

Hello
There is no register description for stusb4761 because this USBPD standalone controller is supposed to be used in AC adapter without any MCU.
NVM of STUSB4761 can be customized in order to change PDO number and content and we do request to use our tool to generate the NVM map.

Then we provide different way to 'reflash' stusb4761.
Without checking the cable, an USBPD controller shall never provide more than 3A in its source cap, as cables are mandated to sustain 3A min. Not all cables can sustain 5A.
To get more than 3A in src_cap, please note that Vconn pin needs to be supplied AND cable needs to be e-marked.

Best regards

Nathalie

MKN
Associate II

@NBALL wrote:

There is no register description for stusb4761 because this USBPD standalone controller is supposed to be used in AC adapter without any MCU.


But some of your Customers want to use the STUSB4761 in an MCU application.

We reconfigure the 4761 on the fly during operation in an multiport USB charger, but we have to reverse engineer every single bit we have to set.

This is not what I'm expecting when I choose ST.

NBALL
ST Employee

Hello
As mentioned in our datasheet, I2C is to configure stusb4761 internal non-volatile memory (NVM).

NVM is not a I2C register map, it cannot be written infinite number of time. That's why we do expect to have STUSB4761 NVM configuration setting done once and not to try to change NVM on the fly.

Best regards

Nathalie