CYPD3177 FAULT line - Stuck high?

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DaFu_4782656
Level 1
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Hi,

we've been using the CYPD3177 for a while. Mainly because it allows to set USB-C PD without any FW development.

The FAULT pin on the chip seems to be constantly high, although the chip is correctly providing power to the whole system (15V @1A). We're puzzled by this and haven't been able to find the root cause. We suspect there's somehow a brief OVP event at some point during startup.

We're wondering: case of a brief OVP event, does the FAULT pin get stuck high? Or does it go back to low as soon as the OVP event disappears?

The datasheet doesn't offer much detail on this.

Thanks.

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1 Solution
YiZ_31
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Hi,

FAULT pin goes HIGH when

(a) Power adapter does not advertise compatible PDOs

(b) VBUS is out of (vbus_min, vbus_max) range

If an OVP event happened, CYPD3177 will send hard reset to the source. It the retry still fails, it will shut down the VBUS gate. You can never get power to the system if an OVP state is not cleared.

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5 Replies
YiZ_31
Moderator
Moderator
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1000 replies posted 750 replies posted 500 replies posted

Hi,

FAULT pin goes HIGH when

(a) Power adapter does not advertise compatible PDOs

(b) VBUS is out of (vbus_min, vbus_max) range

If an OVP event happened, CYPD3177 will send hard reset to the source. It the retry still fails, it will shut down the VBUS gate. You can never get power to the system if an OVP state is not cleared.

Awesome, thanks for the reply, it's helpful!

I guess we're only left wondering why the system can still get power (at the PDO we requested), while the FAULT LED stays on.

Do you think there's some other corner case we left out?

From what you wrote, it sounds like an OVP state can only be cleared by retrying (and succeeding) in negotiating a PDO.

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YiZ_31
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Hi,

Is it possible for you to capture the cc log or read its status register via I2C? That can gives us some clue about what happens.

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At this stage, I'm unable to do that. I'll follow up if I find a way.

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DaFu_4782656
Level 1
Level 1

My bad, the pin is behaving correctly. I'm marking this as answered.

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