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USB Hosts Hubs Transceivers

dkurgs
New Contributor

Hello all,

we are trying to design a USB-C powered device which will need more than 5V 3A of power. The PD communication and control will be handled by an external PD controller, but the USB data will be managed by HX3.

I am not so knowledgeable about the USB Billboard class requirements, but is an external billboard necessary if the HX3 is present?

Consider this example:

The device requires a 9V 3A PD contract for operation, but this can't be supplied by the host. Instead, the host negotiates a 5V 1.5A contract and the PD controller activates a GPIO indicating that a billboard device is required. Can the HX3 react to this GPIO and display the necessary information required by the USB standard to the host PC? If not, is an external billboard device required on one of the HX3 USB 2.0 ports for this?

Thank you!
Daniels

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1 Solution
Sananya_14
Moderator
Moderator

Hello Daniels,

The CCG4 UFP can be configured as a sink as well with a VBUS consumer path in the design since it has dead battery terminations in some of the parts. 

As per the Billboard spec, "If the failure has occurred due to lack of sufficient power while in the AUM, the Billboard Device should set the bmConfigured field to 11b and the bAdditionalFailureInfo.bit0 to 1b. This failure can occur at any time while in an Alternate Mode. Following are possible scenarios where this may occur:
• The AMA requires more power and attempts to negotiate this via [USBPD] but this fails.
• The power contract has been negotiated via [USBPD] with mismatch and the AMA can’t fully function."

So my understanding is that the Billboard interface is expected to be exposed to the host when the device has entered the alternate mode after the PD negotiation but doesnt have sufficient power to function correctly.

Best Regards,

Sananya

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3 Replies
Sananya_14
Moderator
Moderator

Hello Daniels,

Yes, external billboard device would be necessary with HX3 as it cant enumerate as a device on any of its ports. The HX3 firmware is fixed and hence you would require a device to be connected on any of the ports to be able to detect the GPIO toggle from the PD controller and allow Billboard device enumeration. Please refer to the CCG4 Dock reference design which has CY7C65219 connected to HX3 for programming and as a billboard device.

For your use case, I dont think Billboard device is necessary since you arent using any alternate mode. Please also check this KBA.

Best Regards,

Sananya

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dkurgs
New Contributor

Hello Sananya,

thank you for the quick reply! To comment on the CCG4 design, we would be using the Upstream facing port as a sink only, since the application will be bus-powered by the host. I will look at the design more closely though.

My last question is then: if insufficient power can be sourced from the PC host to the device for fully functional operation, isn't a billboard warranted in that case? We do not have a defined alternate mode for our application, only a minimum required PD capability of, say, 25W.

Thank you!

Daniels

0 Likes
Sananya_14
Moderator
Moderator

Hello Daniels,

The CCG4 UFP can be configured as a sink as well with a VBUS consumer path in the design since it has dead battery terminations in some of the parts. 

As per the Billboard spec, "If the failure has occurred due to lack of sufficient power while in the AUM, the Billboard Device should set the bmConfigured field to 11b and the bAdditionalFailureInfo.bit0 to 1b. This failure can occur at any time while in an Alternate Mode. Following are possible scenarios where this may occur:
• The AMA requires more power and attempts to negotiate this via [USBPD] but this fails.
• The power contract has been negotiated via [USBPD] with mismatch and the AMA can’t fully function."

So my understanding is that the Billboard interface is expected to be exposed to the host when the device has entered the alternate mode after the PD negotiation but doesnt have sufficient power to function correctly.

Best Regards,

Sananya

View solution in original post