How to safely power the Pi 4, more specifically:

  1. What voltage levels are safe to power the Pi 4 via the USB-C connector or via the GPIO header?

  2. What are the current requirements?

  3. What Power Management ICs / voltage regulators are used by the Pi 4? The official schematics seem to lack a description of U2 and U3.

  1. Voltage level

The power management IC (PMIC, see section 3) is a MXL7704 with an input voltage range of 4.0 V to 5.5 V and an absolute maximum rating of 6 V that must not be exceeded.

Considering that the downstream USB ports are directly connected to the 5 V power rail the 5 V supply should also comply with USB electrical specifications: 4.45 V to 5.25 V (USB 3.0)

(TBC): Furthermore the "Power good" pins of the PMIC used on the Pi 3B+ (and thus likely on the Pi 4 too) was used to trigger the low voltage warning at 4.63±0.07 V (Raspberry Pi Power Limitations).

The reasonable voltage range to power the Pi therefore is: 4.7 V to 5.25 V

  1. Current requirement

Raspberry Pi 4 spec recommends a 3 A supply (15 W), with a minimum current of 2.5 A if downstream USB peripherals consume less than 500 mA in total.

  1. PMIC

The Foundations blog shows this picture of the power management section on the PCB. The PMIC is a MXL7704 - the same IC is used on the Pi 3B+.

enter image description here

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  • FYI: The original Pi 4 has a non-compliant USB-C power port implementation. Smart power adapters which use "e-marked" cables with chips to negotiate power may not work. Ars Technica: "Raspberry Pi admits to faulty USB-C design on the Pi 4" – l --marc l Dec 29 '19 at 0:31
  • @l--marcl yes, thanks. There are some other questions around here about the USB-C port, feel free to post an answer about this issue there if it is not already addressed. – Ghanima Dec 29 '19 at 8:36

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