Other Parts Discussed in Thread: PMP41115, , TPD4S480, TVS2200
Tool/software:
Hi,
I hope you all are doing well.
I have created a schematic (attached) for a 240W USB-C sink only application using the TPS26750, and it would be very helpful if someone could review it before I send it off for prototyping to ensure its safety.
It closely follows TPS26750EVM, apart from the bidirectional power switch, which is based on PMP41115 - however, the two are very similar, and I decided to use the PMP41115 bidirectional power switch schematic because it seems to save on board area a little bit. I will be programming the EEPROM with a cheap USB programmer (CH341A-based, a newer PCB variant which outputs the correct voltages) which will both power and program the EEPROM while it is mounted on the PCB - this will be done with only 3.3V signals, however, I am not sure if programming the EEPROM in-circuit will cause any issues since it will also be powering LDO_3V3. It would be great if someone could confirm this with me
I would like to be able to use this 240W sink in 'dead battery safe mode' as described in page 11 of the TPS26750EVM user guide, which allows for the core of the TPS26750 to be used without an external supply, as the 3.3V and 1.5V regulators can be powered by a voltage divided VBUS of around 24V max from the TPD4S480 (as far as I'm aware). Is this implementation correct, and is there any special considerations (that is, in programming or hardware) that I have to consider when operating in this mode? Should Q1 be a little bigger to ensure there is not excessive heating?
Also, this is not a very important question for me, but I would like to know - what is the behaviour of TPS26750 when there are no PDOs that match what is requested? Is this something that can be set in the Application Customisation tool? For example, if the required sink power is set to 240W in the USB PD application customisation tool, and the PDOs of the source only go up to 140W, will it let through that 28V or close the power switch?
Thank you so much for your support.
Kind regards,
Rain