The Raspberry Pi 3+ and 4 DC power input is handled by the MaxLinear MXL7704 power management IC (PMIC). A yellow lightning bolt is GPU-superimposed on the Raspberry Pi display output for low voltage. In general computing platform operation is not guaranteed with voltages out of tolerance. The SD card can become unreadable, the Pi may have random malfunctions, and corrupt data (bad writes) on the SD card. 2.5 Amps is the minimum recommended Raspberry Pi power supply current rating, but 3.0 Amps is better if using peripherals (hats). The cable between the power supply and Raspberry Pi must be of good quality to minimize voltage drop and unstable operation. The Raspberry Pi 4 USB-C power connector is markedly more robust than the micro-USB power connector of legacy Raspberry Pi models.

Power Management IC: the APX803 is a simple DC input voltage monitoring IC. Raspberry Pi model 1, 2 and 3 used custom circuitry instead of a COTS PMIC to handle sequencing of discrete DC power input to the Pi subsystems. The significant current demands of the Raspberry Pi 3+ and 4 helped drive the choice of the MaxLinear MXL7704.

It has been noted that damaging the PMIC can make the Raspberry Pi too difficult to repair.

Low voltage alarm: If the DC input voltage falls below 4.65 volts, the GPU superimposes a lightning bolt graphic on the display output. This may not be visible on a VNC remote desktop.

Measure DC input: There is no built-in capability to measure the Raspberry Pi DC input voltage without adding an external ADC. It is possible to read the input voltage state (OK/low) from the Terminal:

• Raspberry Pi 1 B+, 2: read state of GPIO 35.
• Raspberry Pi 3: read GPU-driven LED status.

When compiling programs with concerns about excessive power consumption, consider not compiling in parallel. For make, make -j2 uses 2 CPU cores for example–omit the -j option to compiler with 1 CPU core.

• Detailed Raspberry Pi voltage/current measurements
• Power recommendations for each Raspberry Pi model.
• Pi power alarm LED controlled with software since it’s on GPIO.

Related: Measure Raspberry Pi CPU temperature