On my circuit board, I have three different voltage regulators. I have a 5V Buck converter that goes into a 3.3V LDO and then finally 1.8V LDO. When I power the board with a USB and do not use external power, I get a good 1.8 Volts on the output of the 1.8V voltage regulator.
When I use external power, I get 3.26 Volts output on the 1.8V voltage regulator. My design is already extremely noisy, which I will be fixing on the next design. My questions is, can excessive noise on the 3.3V rail cause a voltage regulator to output 3.3 volts? Or is there something else going on here?
I am using the TLV702 Voltage Regulator. DataSheet