RotoPD Pro 240W AP33772S ?

[jbeaudoin11]

Hi, me again, just been curious about your message in #7 concerning the RotoPD Pro.

I saw the new hackaday page and got confused. (Tried commenting directly there but hackaday is just not letting me...)

The AP33772S doesn't support 240W and I don't see any Diodes compatible chip so i assume you're going to work with something else ? Did you guys figured out the HUSB238A from your previous project and intend to use it in the Pro ?

[centydev]

We design a work around circuit for the AP33772S. So some draw back is we will be losing the VBUS and current reading. We are considering adding back a INA236 current monitoring IC to get back the lost feature. Wonder if you have any thought on this.

We just tried again for the HUSB238A last month and just keep getting inconsistent result even for acquiring basic profile. So we will abandon that IC entirely.

[jbeaudoin11]

Looking back at the documentation and my notes, i guess the protocol allows it :
PD_REQMSG.VOLTAGE_SEL -> 8 bits 200 mv/bit in AVS -> 51V (care 0xFF is treated as MAX not 51V).

So on paper it should allow for 48V and i guess you actually tested it out in your demo ? I guess it's really just an IC limitation :

Operating Voltage Range of VCC: 3V to 31V
Support PD3.1 EPR/AVS Up to 28V and SPR/PPS Up to 21V
VBUS Short Protection on CC1/CC2 Pins Up to 34V

28V is the closest AVS standard value so it kind of make sense as why they advertise it like that.

---

So you guys think you can make some work around the vbus and allow 48V@5A/240W ?

So some draw back is we will be losing the VBUS and current reading

I'm assuming you will lose more than that like all the protection features (under/over voltage, over current , over temp, derating). We for sure need an alternative to the VBUS control and current/voltage monitoring. Protections could be shift to the MCU but it's making things a bit more complex.

This board is more for hobbyist, it's easy to cut corners but in the end, the more someone is "incompetent" the more they should be protected from themselves so i don't know if it's such a good idea. Sure the chip is called "Pro" but you know i'm gonna be the first to f*ck blow something up 🙃.

Here's a thought.. What if you were to add a super cheap mcu like a ch32 on the board and offload a lot if not all lost capabilities to that chip ? You could make an AP emulator firmware which the external MCU can interface against using the same libraries. It opens up a lot of possibilities.. One thing i was gonna request is to add a way to change the i2c address, that's one way to do it i guess.

Adding a ch32 sure make this project much bigger in scope but it could make a pretty cool module with extended capabilities. Alternatively, instead of a ch32, you could go the pico route too ($$) and combine your projects... I'm sure you get the gist.

Anyways, really depends on where you guys wanna go with this but imo crippling the AP33772S basic capabilities to get 48V is not a good trade off. Would probably not buy it if i don't get vbus control and current/voltage sensing. Sure i can give up the protections.