I am looking at the data sheet for the PIC15F1508/1509.
In Table 29-4 you will see that the output high and low voltages are specified at single digit milliamps of current in order to maintain the output voltages within the appropriate logic levels. I would not design for output source or sink currents higher than these.
Looking at the specifications, with Vdd = 5.0 V the maximum output low voltage is 600 mV when sinking 8 mA. This corresponds to an effective on-resistance of the output MOSFET of about 75 ohms. This is a maximum value but suppose the typical was half of that. Then the output on-resistance is about 35 ohms and trying to sink 50 mA would give you an output low voltage of 1.7-1.8 V (while dissipating almost 90 mW in that output transistor). I would not design like that.
For Vdd = 3.3 V and 1.8 V the sink current for 600 mV output low voltage is even less indicating that the output MOSFET is even less enhanced and has an even higher effective on-resistance.
Table 29-1, which give the Absolute Maximum Ratings shows that I/O pins *must* not be operated with source or sink currents greater than 50 mA or the PIC may be damaged. And note that the output voltage, high or low, is *not* specified with currents this high.
post edited by Bob White - 2020/01/15 14:34:07