We are operating the DP83867 in dual power supply mode, powering first the VDDIO power supply rail with 1.8 Volts, followed by simultaneously ramping the VDDA2P5 and VDD1P1 supplies.
The VDDA2P5 power supply is provided by a MCP1726 linear regulator. When this power supply is isolated from the DP83867 load, it starts up normally in approximately 80 us and gives a stable 2.5 Volt power supply. When connected to the DP83867, the power supply linearly ramps up to 3.0 Volts, and then drops down to a stable 2.5 Volts. I have attached a trace of the fault.
We are using a 7499111221A magnetic jack on the DP83867.
Any help you can give with this would be greatly appreciated.
