Microcontroller projects

last updated: 2026-05-15

Quick links

Pico: Maximum current on VBUS

Introduction

What is the maximum current I can safely draw from the Pico's VBUS pin?

65 degree

Naturally the current is limited by the USB power source and the USB cable itself, but modern power supplies can deliver up to 3 A and the PD charge cables are thick enough to transport the 3 A.

The Pico’s official documentation suggest that you should not draw more than a few hundred mA from VBUS to avoid overloading the USB port or the Pico’s PCB traces.

I think it we could draw a lot more than 500 mA as the traces are very short. So let's try it out.

I used the following gear:

The measurements took place in a normal heated room (22 °C). For every temperature measurement I waited 15 minutes for the end temperature to stabilize.

I used an original Pico2 with micro USB connector and a Waveshare RP2350-zero with USB-C connector for my tests.

Resistance

A resistance check before the connector to the pins gave lower values for the original Pico:

Board Resistance 5 V trace Resistance GND trace Overall resistance
Original Pico 32 mΩ 33 mΩ 65 mΩ
Original Pico2 31.5 mΩ 31 mΩ 62.5 mΩ
Waveshare RP2350-zero 55 mΩ 33 mΩ 88 mΩ

Clearly we got a higher resistance for the Waveshare RP2350-zero! So this should also show in the temperatures.

Temperatures Original Pico2

The Pico has a micro USB connector. These connectors are rated for 1.5 A and not for 3 A like the USB-C connectors. We get higher voltage drop on the pins than with the RP2350-zero.

The voltage drop and power are calculated values.

Voltage VBUS Current Voltage drop traces (I*R) Power (I²*R) Temperature
5.12 V 0.5 A 0.033 V 0.016 W 24 °C
5.04 V 1 A 0.033 V 0.065 W 25 °C
4.97 V 1.5 A 0.098 V 0.146 W 26 °C
4.9 V 2 A 0.130 V 0.260 W 30 °C
4.8 V 2.5 A 0.163 V 0.406 W 33 °C
4.73 V 3 A 0.195 V 0.585 W 38 °C
3.9 V 3.5 A 0.228 V 0.796 W 44 °C

Pico HD35     43degree

As expected at 3.5 A the 3 A PD power supply dropped the voltage to 3.9 V

Temperatures Waveshare RP2350-zero

Voltage VBUS Current Voltage drop traces (I*R) Power (I²*R) Temperature
5.15 V 0.5 A 0.044 V 0.022 W 25 °C
5.10 V 1 A 0.088 V 0.088 W 29 °C
5.08 V 1.5 A 0.132 V 0.198 W 31 °C
5.03 V 2 A 0.176 V 0.352 W 37 °C
5.0 V 2.5 A 0.220 V 0.550 W 44 °C
4.94 V 3 A 0.264 V 0.792 W 51 °C
4.00 V 3.5 A 0.308 V 1.078 W 60 °C

RP2350_zero HD35     43degree

Conclusion

If you draw more than 500 mA, you do so at your own risk, of course. The tests are not universally applicable, as poor solder joints or similar issues may cause the temperature to rise.

But I think if you use VBUS while programming for tests e.g to power WS2812b RGB LEDS and draw up to 3 A there is no real issue. The absolute maximum temperature was 65°C at one setup. If you stay physically with the material you can intervene if it starts to smell funny :).