Help understanding USB-C controllers

[Rickkap]

I need help trying to understand how the USB-C controllers work on a PC laptop.

I have an Asus Notebook PC model:UM425I which doesn't turn on. I check the motherboard and is doesn't have any liquid damage as such.

The USB-C tester is showing 5.18 - 5.19v fluctuating 0 amps and that's on both ports.

I checked the coils and there is no short to ground, only one was low in diode mode and with this removed the tester shows the exact same voltage readings.

There is only one USB-C controller (INFINEON CYPD5225-96BZXI) Link to the datasheet (https://uk.farnell.com/cypress-semic...-to/dp/3259951) This has been replaced but it's still the same.

The only voltages i can see is 3.4v and 1.8v coming out of the controller but these aren't going to the BIOS, iTE or any other components.

On the datasheet it mentions that this controller has 32-bit MCU Subsystem ■48-MHz Arm Cortex-M0 CPU ■128-KB Flash ■12-KB SRAM

Could it be that it needs to be programmed to be able to switch to 20v?

I would also be grateful if someone could explain from inserting the charger and it showing 5v to it switching to 20v and what components are needed to achieve this.

[mon2]

Re: Help understanding USB-C controllers

Post a pic of your usb c meter. Is it a bidirectional type?

With 0A current draw, the board is not consuming any current so not powered.

Google power delivery tutorials to understand this operation. The motherboard and adapter exchange data packets across a single wire interface to understand what the adapter can supply. The power delivery controller will then select the best voltage and current for its requirements.

Yes the pd controller is blank upon purchase and requires firmware to invoke the power delivery contracts. From my understanding you are in a catch-22. To reflash this firmware in system, the motherboard needs to boot. Otherwise you will need to reflash using an external adapter from cypress / Infineon.

Check their website and user forums for advice. Update this thread.

[Rickkap]

Re: Help understanding USB-C controllers

Thanks Mon for your reply.

Yes it is bidirectional and i will post a pic tomorrow.

I don't think there's much hope for this laptop as it's a BGA chip and i don't have a CY8CKIT-005 programmer.

[reformatt]

Re: Help understanding USB-C controllers

I'd return the original PD controller back because as Mon2 said, it needs to be programmed. It's unlikely to be the cause of your fault, as most port faults tend to be the port controller IC itself (and you'd get different responses between ports).

You need to understand that 20V negotiation isn't entirely dependent on the PD controller, as it relies on other power rails from the laptop to do that. You at least need your 5V to provide logic supplies such as 3.3V etc, and without these you won't get your 20V.

For example, a Lenovo L380 was brought to me recently with the same fault. No 20V, both ports stuck on 5V. USB-C section had been extensively reworked at another repairer and had given up. The PD controller had a number of missing power rails, and when chased through, the 5V didn't even get to the internal supplies due to a shorted cap on the main power rail after the first two MOSFET's. Once the cap was removed, the laptop burst into life and we had our 20V. MAC's pretty much do the same thing when you have a short on PPBUS_G3H.

Given it's an Asus, I doubt you have a schematic. I'd be looking for a short on the main power rail around the current sense resistor first. Asus pretty common to have caps just go short.

[Rickkap]

Re: Help understanding USB-C controllers

OK so i switched the PD controller back and after searching i found a short on a coil/MOSFET. After applying a very small voltage the CPU is the culprit.

Dead board. Thank you for your help