Trrs spec - audio jack
You have somewhere between 100 and 500 microamps according to the OMTP Local Connectivity Wired Analogue Audio specification.


  The electrical characteristics of the audio Terminal of the  Terminal SHALL operate within the values stated below:    Bias Current Min 100 µA Max 500 µA  (Voltage of 2.1V generated over microphone component with  serial pull up resistor value between 1.90 kΩ and 2.2 kΩ)  Usage sensitivity Min -62 dBV   The measurement of the electrical characteristics SHALL be  done in accordance with the standard publication  IEEE Std  269-2002 [4]