Why the Official Raspberry Pi 4 Power Supply Provides 5.1 Volts Instead of 5

The official Raspberry Pi 4 power supply provides 5.1 volts instead of the standard 5 volts for several reasons. This article delves into the benefits and design considerations that led to this decision.

Voltage Drop Compensation

When powering devices, voltage can drop due to cable resistance and other factors. By providing 5.1 volts, the power supply ensures that the Raspberry Pi receives a stable 5 volts even if there is some voltage drop along the power cable. This is crucial for maintaining the performance and reliability of the device.

Power Requirements

The Raspberry Pi 4 has higher power requirements compared to previous models, especially when using peripherals or under heavy load. The extra 0.1 volts help ensure that the board operates reliably under these conditions. This additional voltage provides a margin of safety, ensuring that the board can handle unexpected increases in load without performance degradation.

USB Power Specifications

USB specifications allow for a small tolerance in voltage. 5.1 volts is within acceptable limits for USB power supplies. This slight increase helps maintain performance without exceeding safe operating conditions for the device. By operating at 5.1 volts, the Raspberry Pi can ensure compatibility with a wider range of USB devices without risking damage.

Thermal Management

The additional voltage can also contribute to better thermal management. With 5.1 volts, the Raspberry Pi can draw enough power for its components while minimizing the risk of overheating. This is especially important for the more powerful Raspberry Pi 4, which has a higher power draw compared to its predecessors.

It's worth noting that no component on the Raspberry Pi 4 board is driven directly by 5V. The highest rated onboard component is likely driven by the 3.3V SoC core voltage. All these lower voltages are obtained by a step-down converter from the input 5V, which can handle a range of 4V to 6V. This design choice allows for flexibility in power supply while maintaining the reliability of the board.

However, the main concern with a non-5V supply would be the compatibility of USB devices connected to the Pi. Most USB devices are designed to work within a certain voltage range, and deviating too far from 5V might cause issues with some peripherals. Therefore, the official 5.1V power supply is carefully designed to strike a balance between reliability and compatibility.

In conclusion, the decision to provide 5.1 volts for the Raspberry Pi 4 power supply is a result of multiple factors, including voltage drop compensation, power requirements, USB power specifications, and thermal management. This design choice ensures that the Raspberry Pi 4 operates reliably and maintains optimal performance under various conditions.