Yes, it will fall back to legacy charging and check for the current capability on the DP/DM lines. The fault detection should work based on the VBUS_MIN and VBUS_MAX setting so in this case 5V can be set.
If you connect to only a Type-C capable charger, it will pass 5V and not have any PD negotiation with the device.
I have a related problem with the BCR. The system we are designing requires 20W+, so I am hoping to use the FAULT pin to detect when a user tries to use an under-powered USB charger, including type-C non-PD chargers. I have swapped out resistors on the voltage dividers to read as follows:
VBUS_MAX: 5k/NC (pull-up/pull-down), unchanged
VBUS_MIN: 5k/1k (9V min)
ISNK_COARSE: 5k/5k (3A)
ISNK_FINE: NC/5k (0mA)
Test points were read on a multimeter (text is pretty small, so I hope I'm hitting the right test points):
TP7: 3.389V (VBUS_MAX)
TP8: 0.557V (VBUS_MIN)
TP6: 1.696V (ISNK_COARSE)
TP9: 0V (ISNK_FINE)
However, when I try to use a standard type-C connector, the FAULT LED does not light up, nor does the voltage on TP3 is high (3.4V). I expected the FAULT pin to alert since my minimum voltage was set to 9V, but it does not. I get 4.8V on DC_OUT and 0V on SAFE_5V_OUT.
What am I missing?
I have been able to probe the I2C addresses outline in the HPI specification. For example, with the standard type-C adapter, the Current PDO and Current RDO (0x1010 and 0x1014) both read all zeros.
When I use a PD charger, i get 15V on DC_OUT, 0V on SAFE_5V_OUT. The current RDO reads 0x0004B12C, and the current PDO reads 0x4004B12C.
Again, what am I missing?
Any advice you can provide would be greatly appreciated.