Problem with the CCG3 PA ramping to 15V and 20V.

[StPa_4486781]

The CCG3 PA is configured for 5V, 9V, 15V, and 20V all at 2.5A.  For all 5V and 9V tablets, the CCG3 PA  negotiates as expected, and the voltage and current are as advertised.  For 15V devices, some work and some do not.  Lower power devices that can also charge at 5V will charge at either 5V or 15V successfully.  Higher power devices that require 15V will not.  In this case the voltage attempts to ramp up from 5V, but only reaches about 5.8V before the CCG3 PA appears to reset.  It then just cycles in and out of reset indefinitely.  The same is true of 20V.  The hardware has been tested, and is functioning correctly.  It appears as though something is preventing the voltage from ramping.  Testing with another USB C PD supply shows that the current draw is less than 2.5A on these devices.  Has anyone else seen this issue?

[MallikaK_22]

Hi,

>> What kind of hardware are you using? Is it our CY4532 Evaluation board or your custom board?

If you are using the custom board please share the schematics.

>> Which example firmware are you using?

>> Can you please share the CC logs if you are using the EZ-PD Protocol Analyzer?

Best Regards,

Mallika

[StPa_4486781]

Mallika,

It is a custom board.  What we have found is that it actually functions correctly and charges small tablets at all of the advertised voltages.  It only faults when dealing with higher power tablets.  Further investigation has shown that we are violating the USB C voltage rise specification with the current settings.  I did not do the coding so I do not know the exact settings, and the engineer who does is out until Monday.  Here is what I see, though.

USB C specifies a max slew rate of 30mV/us.  I measured the rise time of our system from 5V to 15V and it was equivalent to 60mV/us.  We are using a direct feedback system to a 4A buck switcher.  The 100nA current step yields a 22mV voltage step.  Based on that, I am thinking that I want a Vbus transition up step of about 275us to slow the rise down to about 180ms.  Right now the rise is only 160us.  My suspicion is that that will resolve the problem if higher power tablets have more bulk input capacitance which likely cause the switcher to current limit while trying to transition that fast.

Are there any other power settings that I should look at?  I assume that for direct feedback I should set synchronous rectifier to OFF.   I also don't know how to set Vbus Source Drive strength.  Any guidance on the proper settings would be appreciated.

Best,

Steve

[MallikaK_22 · Accepted solution]

Hi Steve,

Apologies for the delay in response.

Your understanding is correct regarding the maximum slew rate for positive voltage transitions defined as 30mV/us as per the USB-PD spec.

This could be the reason for getting a timeout which could be causing the reset. You can try changing the rise time in your system to meet the specification.

Regarding the other power settings, you can follow the settings done in the CYPD3175-24LQXQ_pa_direct_fb.

Also, please have a look at section 3.2, Updating CCGx Configuration (Table 1- Power Settings) in the CCGx Power SDK User Guide https://www.cypress.com/documentation/software-and-drivers/ez-pd-ccgx-power-software-development-kit

You will find the parameters such as VBUS source Drive Strength, Synchronous Rectifier and other Power Settings parameters mentioned there which can be customized as per your requirements.

Regards,

Mallika