The Pico and Pico 2 boards use an RT6150B-33GQW regulator to provide 3V3. The datasheet I have for that includes a graph which shows Maximum Output Current of 300mA (at 1V8 input) to about 1500mA (at about 4V25 input), dropping to about 1400mA at about 5V - Unfortunately the supplied graph isn't very clear nor does it have useful voltage and current values on each axis.
So, as said it will depend on input voltage and load. I don't know what Raspberry Pi's recommendation to keep draw below 300mA is based upon but it's technically correct even if it may need to be well below 300mA with low input voltage.
Maximum Power Dissipation comes into it as well.
So it's not easy to give a simple definitive answer.
Someone could determine more detailed data for typical USB use with no load, and similar at various VSYS voltages. I would have expected the Pico and Pico 2 datasheets to already include that data but they don't. You could raise a feature request to have it added.
What is your external circuit drawing, or what is your existing external 3V3 regulator rated for ? If it's 100mA at 5V input I expect you can drive your circuit from the 3V3OUT, maybe even if rated at 250mA.
So, as said it will depend on input voltage and load. I don't know what Raspberry Pi's recommendation to keep draw below 300mA is based upon but it's technically correct even if it may need to be well below 300mA with low input voltage.
Maximum Power Dissipation comes into it as well.
So it's not easy to give a simple definitive answer.
Someone could determine more detailed data for typical USB use with no load, and similar at various VSYS voltages. I would have expected the Pico and Pico 2 datasheets to already include that data but they don't. You could raise a feature request to have it added.
What is your external circuit drawing, or what is your existing external 3V3 regulator rated for ? If it's 100mA at 5V input I expect you can drive your circuit from the 3V3OUT, maybe even if rated at 250mA.
Statistics: Posted by hippy — Thu Feb 12, 2026 3:05 am