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USB EZ-PD™ Type-C Forum Discussions

MaRe_4701411
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Hello,

This is related to another question that was answered on the forums.  I've posted this question there as well, but I wasn't sure if that post would get traffic, since it's been answered.

I have questions related to the FAULT pin behavior on the BCR when a legacy non-PD type-C supply is attached.  The system we are designing requires 20W+, so I am hoping to use the FAULT pin to detect when a user tries to use an under-powered USB charger, including non-PD type-C chargers.  I have swapped out resistors on the voltage dividers to read as follows:

VBUS_MAX: 5k/NC (pull-up/pull-down), unchanged

VBUS_MIN: 5k/1k (9V min)

ISNK_COARSE: 5k/5k (3A)

ISNK_FINE: NC/5k (0mA)

I've also set the rotary switch to position 5 (NC).

Test points were read on a multimeter (text is pretty small, so I hope I'm hitting the right test points):

TP7: 3.389V (VBUS_MAX)

TP8: 0.557V (VBUS_MIN)

TP6: 1.696V (ISNK_COARSE)

TP9: 0V (ISNK_FINE)

However, when I try to use a legacy non-PD type-C connector, the FAULT LED does not light up, the voltage on TP3 is high (3.4V), and the FAULT pin remains at 0V.  I expected the FAULT pin to alert since my VBUS_MIN is set to 9V, but it does not.  I get 4.8V on DC_OUT and 0V on SAFE_5V_OUT.

What am I missing?

I have been able to probe the I2C addresses outline in the HPI specification.  For example, with the legacy non-PD type-C adapter, the Current PDO and Current RDO (0x1010 and 0x1014) both read all zeros.

When I use a PD charger, i get 15V on DC_OUT,  0V on SAFE_5V_OUT.  TP3 reads 13.79V. The current RDO reads 0x0004B12C, and the current PDO reads 0x4004B12C.

Again, what am I missing?  My VBUS_MIN is set for 9V minimum, but when I use a 5V-only charger, the BCR does not throw the FAULT.

Any advice you can provide would be greatly appreciated.

Regards,
Matt

1 Solution
YiZ_31
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Hi,

For the legacy USB Type-C to Legacy Cable Assemblies integrates Rp, BCR will recognize it as a dummy source. The proceduce follows Type-C specification not PD Specification. So the PDO set won't work in this situation. The default 5V provided will not be recognized as a fault condition.

Regards,
Eddoe

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MaRe_4701411
Level 1
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First like received

As a follow-up, I just tried a 3rd source, this type the TYPE-C output from my laptop.  With that source, the FAULT LED does light up, DC_OUT goes to 0V and SAFE_5V_OUT reads 5V.

To elaborate, the "legacy non-PD type-C" source that I first tried, was an A-to-C cable plugged into a USB hub.  The cable was one I just had lying around, so I cannot say what its capabilities are.  The cables used with my laptop (which shows a FAULT) and my PD charger (which throws no FAULT and outputs 15V) were both 100W C-to-C cables with E-Marker which I purchased specifically for high-power capability.

I'm not sure if this helps, but I wanted to provide all the information I know.  I am still concerned that my legacy 5V-only source does not throw a FAULT.

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YiZ_31
Moderator
Moderator
Moderator
1000 replies posted 750 replies posted 500 replies posted

Hi,

For the legacy USB Type-C to Legacy Cable Assemblies integrates Rp, BCR will recognize it as a dummy source. The proceduce follows Type-C specification not PD Specification. So the PDO set won't work in this situation. The default 5V provided will not be recognized as a fault condition.

Regards,
Eddoe

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Thanks for the clarification.  It's unfortunate that the chip wasn't designed to recognize that as a fault.  Seems like a pretty common scenario.  We'll work around it.  Thanks again.

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YiZ_31
Moderator
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Hi,

As I know BCR is expected to have firmware update later this year. Hopefully this issue will be solved.

Regard,s
Eddie

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Very interesting.  Is there a mailing list or other means to be informed of this update when it's released?

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MaCa_4691661
Level 1
Level 1

Hi,

I'm also interested in knowing when the new firmware is released.

I am having a similar problem.

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