About this component
Turns the 5 V input into the 3.3 V, 1.8 V, DDR and SoC core rails, with the core buck voltage adjusted over I2C for dynamic voltage scaling. A Pi 4 with the red power LED on but no boot activity, or one that gets hot near this chip with no output, is often a PMIC or shorted-rail fault; measure each buck output against ground before replacing it. MaxLinear lists the MxL7704 as end of life. Part variants: The exact ordering variant (AQB/XQB) used on the Pi 4 is not documented publicly. On the 8 GB model one external switch-mode supply was moved to a new position beside the USB-C connector.
What it does on this board
Power-management IC for the SoC rails.
Pinout & readings
Pinout and readings are for members
Create a free account to see the test data for U5 (MxL7704):
- The full pinout — 33 pins with what each one does
- Datasheets