CYPD3177 EZ-PD : Fault pin does not trigger when used with USB-A (5V only) chargers

[magr_4749171]

Hi,

We are using the CYPD3177 EZ-PD as a DC barrel replacement, the application is marketed for.

Our target application requires a 20V, 90W supply (i.e. 20V & 4.5A or greater.)

We have configured the CYPD3177 using external resistors as follows:

20V supply, 4.5A or greater.

VBUS min = Rtop 0R, Rbot open = 20V minimum

VBUS max = Rtop 0R, Rbot open = 20V maximum.

Isink_Coarse = Rtop 5k1, Rbot = 10k = 4A.

Isink_Fine = Rtop 5k1, Rbot = 2k4 = 0.5A

1. Plug in a USB-C supply with the correct power rating, Fault line is low as expected, 20V is present to the application. Expected Behaviour.

2, Plug in a USB-C supply with underated current, Fault line is high, No voltage is presented to the application. Expected Behaviour.

3, Plug in a USB-A 5V supply with USB A-C cable, Fault line is low, 5V is presented to the application!

The datasheet clearly states:

"Pin 9 - FAULT - The EZ-PD BCR device pulls this line high if the power adapter cannot supply the required voltage or current "

I can almost understand if the chip was configured to allow 5V, then it might decide to let 5V though without negotiation.

But with 20V set as a minimum it should not let any power though without completing power negotiation.

Is this a know bug?

We have detected this behaviour during verifiaction and so need a resolution as soon as possible.

Please advise.

Mark.

[MallikaK_22 · Accepted solution]

Hi,

For the legacy USB Type-C to Legacy cable assemblies which have Rp termination integrated, BCR will treat it as a non-PD source.

So the working will be as per the Type-C specification and not the PD specification, i.e. the PDOs set don't work in this situation. This means that the device wont be checking for FAULT condition based on configured PDOs and actual voltage from source.

Hence, the default 5V provided will not be recognized as a fault condition.

Best Regards,

Mallika