STI3474 (S43BoEA) for Whatsminer M20 M30 series Control Board

STI3474 (S43BoEA) 0.8V 3A Step-Down Converter – Whatsminer M20 / M30 Control Board Repair

The STI3474 (marking S43BoEA) is a high-efficiency 0.8V / 3A synchronous step-down converter switching at 600kHz, used on the Whatsminer M20 and M30 series control boards. It accepts an input range of 3.5V to 18V and features PWM/PFM automatic mode switching for efficient operation from full load down to light load, slope-compensated current mode control with internal compensation, and synchronous rectification that eliminates the need for an external Schottky diode.

Role on the Whatsminer Control Board

The STI3474 generates the 0.8V core supply for the control board's processor and logic ICs. When it fails, the core voltage rail collapses and the control board stops booting — the miner goes offline with no network presence and no hashboard communication. Because the 0.8V rail is the lowest-voltage and highest-current local supply on the board, it is the most thermally stressed regulator and the most likely to degrade over time.

Replacement Procedure

Remove the control board and locate the STI3474 near the processor area — it is a small IC marked S43BoEA. Measure the output pin: it should read 0.8V; an absent or unstable reading confirms failure. Desolder, clean pads, install the new device with pin 1 aligned and reflow. Power on and verify 0.8V on the output, then confirm normal boot, network connectivity and hashboard detection.

STI3474 Step-Down Converter Specifications

Related Whatsminer M20 / M30 Control Board Components

• STI3472 Step-Down Converter – Whatsminer Control Board
• Whatsminer CB4 V10 H6 Control Board – M20 / M30 / M31
• Whatsminer Adapter Board – M20 / M30 Controller
• 14-Pin Test Fixture Cable – M20 / M30 / M31 / M32

Repairing Whatsminer control boards? Contact us at contact@lys-sz.com for voltage regulators, CPUs and all board-level components.

Worldwide shipping from our Shenzhen warehouse.