Using the eval board, I have charged several different Apple devices but I not recorded more than 1.5A charging current. The devices are iPhone 12 Max, iPhone Xs, iPhone 6s Plus, Ipad pro (9.6" old model), and iPad 8th gen.
I powered the eval board (one power method at a time) from the 7-18V input (at 9V) and without the on-board DC/DC by powering with +5V on J4-2 and GND on J6-2. The CTL3-1 signals are set for DCR HI. ILMI_HI resistor is 19.1k-ohms.
My DC supply indicates approximately 1.5A charging for both power input types - math is required to estimate 1.5A output with the 9V input. If I add an ammeter inline with the USB cable, the charge current drops to 1A. The 1A current is observable by the DC supply current monitor also. Long, lossy cables also result in 1A charging, as reported by the DC supply - no inline ammeter for this measurement. I observe that slightly increasing the voltage causes the current to approach 1.5A. The D+/D- pins each measure 2.7V to GND, so it appears that the divider3 circuit is active and always on.
Should I be able to achieve > 1.5A charging current on Apple devices when using TSP2549 (Q1 or non-Q1)? Note that the eval board uses TPS2549Q1RTE rather than TPS2549RTER/T. I assume the "Q1" part is equivalent functionally to the non-automotive part, but I do not see any data at the website about the "Q1" part.