What is powering the new Raspberry Pi 4?
The highly integrated MxL7704 provides all key power rails required by the Raspberry Pi 4, including the low noise voltage rail used for audio circuitry. It also handles the unique power sequencing requirements of each rail with ease due to its convenient I2C programmability. The MxL7704’s I2C interface communicates with the computer’s SoC for dynamic voltage scaling, status monitoring, sequencing control and PGOOD routing. These features enable the Raspberry Pi 4 to save power by dynamically reducing the voltage to the SoC when the system is idle and boosting it when the processor is running at maximum speed.
The MxL7704 includes four synchronous step-down buck regulators that provide system, memory, I/O and core power from 1.5A to 4A. An on-board 100mA LDO provides clean 1.5V to 3.6V power for analog sub-systems. It also features an integrated 8-bit ADC with 2 external inputs and temperature sensor that provide die temperature monitoring, telemetry and additional flexibility. The Raspberry Pi 4 utilizes the MxL7704’s on-board ADC to determine if there is a high current delivery USB power supply. All these features are packed into a small 5x5mm 32-pin QFN package, which helps the Raspberry Pi retain its small form factor.
- Input voltage range: 4.0V to 5.5V
- 4 Synchronous Buck Regulators
- Internally compensated current mode
- 1MHz to 2.1MHz switching frequency
- Buck 1: 3.0V to 3.6V, 20mV step, 1.5A
- Buck 2: 1.3V to 1.92V, 20mV step, 1.5A
- Buck 3: 0.8V to 1.6V, 6.25mV step, 2.5A
- Buck 4: 0.6V to 1.4V, 6.25mV step, 4A
- 100mA LDO: 1.5V to 3.6V, 20mV step
- ±2% maximum total dc output error over line, load and temperature
- 3.3V/5V 400kHz I2C interface
- Dynamic voltage scaling
- Status monitoring by channel
- Sequencing control
- Input voltage status register
- Highly flexible conditional sequencing engine with external input
- 2 configurable PGOOD outputs
- Adjustable switching frequency
- 5mm x 5mm 32-pin QFN package