Buck Converters — Common ICs & Specifications

Overview

Buck converters are the primary voltage regulation topology used on hash boards. They step down the 12V (or 48V) PSU input to the sub-0.4V core voltage required by ASIC chips. Each voltage domain on a hash board has its own buck converter circuit, making these components among the most numerous and failure-prone on the board.

This page covers how buck converters work in the context of mining hardware, the most common ICs you will encounter, and how to test and diagnose failures.

How Buck Converters Work

A buck converter is a switching power supply that converts a higher input voltage to a lower output voltage with high efficiency. The basic circuit consists of four key components:

Core Components

1. Controller IC — Generates the PWM switching signal and regulates the output voltage via a feedback loop
2. High-side MOSFET — Switches the input voltage on and off at high frequency (300kHz-1MHz)
3. Low-side MOSFET — Provides a current path for the inductor when the high-side MOSFET is off
4. Inductor — Stores energy during the on-time and releases it during the off-time, smoothing the output
5. Output capacitors — Filter the remaining ripple to provide a clean DC output

Operating Principle (Simplified)

    12V Input
        |
   [High-side FET] ──── Switching Node ──── [Inductor] ──── Output (0.3V)
        |                     |                                  |
   [Low-side FET]            ───                          [Output Caps]
        |                                                        |
       GND                                                      GND

1. On phase: The high-side MOSFET turns on, connecting the 12V input to the inductor. Current flows through the inductor to the output, and the inductor stores energy in its magnetic field.
2. Off phase: The high-side MOSFET turns off and the low-side MOSFET turns on. The inductor's stored energy drives current through the low-side MOSFET to the output.
3. Feedback: The controller IC monitors the output voltage through a resistor divider. If the output drops below the target, the duty cycle increases. If it rises above the target, the duty cycle decreases.

The output voltage is approximately: Vout = Vin x Duty Cycle

For a 12V to 0.3V conversion, the duty cycle is only about 2.5% — the high-side MOSFET is on for a very short time during each switching cycle.

Common Buck Converter ICs

TPS53647 (Texas Instruments)

The TPS53647 is widely used in Bitmain Antminer S19 series hash boards. It is a single-phase D-CAP+ adaptive on-time controller.

Key signals to probe:

• VIN — Should read 12V (input power)
• VOUT/VSNS — Output voltage (0.28-0.32V depending on model)
• EN — Enable pin, should be HIGH when board is running
• PGOOD — Power Good output, HIGH when output is in regulation
• SW — Switching node (oscilloscope only)

MP2943 (Monolithic Power Systems)

The MP2943 is found in newer Bitmain designs including the Antminer S21 series. It offers higher current capability and integrated driver circuitry.

IR3553 (Infineon)

The IR3553 is a single-phase buck regulator commonly used in MicroBT Whatsminer hash boards.

Unique feature: The IR3553 is a PowIRstage IC, meaning it integrates the high-side MOSFET, low-side MOSFET, and gate driver into a single package. This simplifies the board layout but means the entire power stage must be replaced if any MOSFET fails.

RAA228228 (Renesas)

The RAA228228 is used in the latest MicroBT Whatsminer designs and some Avalon boards.

Specifications Comparison

How to Test a Buck Converter

Common Failures

1. Output Shorted to Ground

Cause: Most often a shorted ASIC chip in the domain, not the regulator itself. The chip failure pulls the output rail to ground, which causes the regulator to overcurrent and shut down.

Diagnosis: Disconnect the regulator output from the ASIC load (by removing the inductor). If the regulator now produces the correct voltage, the short is on the load side.

2. High-Side MOSFET Short

Cause: Electrical overstress, thermal runaway, or MOSFET degradation. The high-side MOSFET fails short, connecting 12V directly to the domain output.

Diagnosis: With the board unpowered, measure resistance from VIN to the switching node. A short (below 1 ohm) indicates a failed high-side MOSFET.

3. No Switching (Regulator Dead)

Cause: Failed regulator IC, missing input voltage, or enable pin held low.

Diagnosis: Verify VIN and EN are present. If both are correct but no switching activity is observed at the SW node, the regulator IC has likely failed.

4. Inductor Open or Saturated

Cause: Physical damage (cracked core), manufacturing defect, or operation beyond saturation current.

Diagnosis: With the board unpowered, measure DC resistance through the inductor. Expected 1-5 milliohms. An open circuit indicates a broken inductor winding.

Replacement Notes

• When replacing a buck converter IC, use a hot air rework station at 260-280°C
• QFN packages have a large thermal pad underneath — ensure adequate flux to achieve full reflow
• After replacement, always verify output voltage with a multimeter before reconnecting the ASIC load
• If a MOSFET short caused the IC failure, replace both the IC and the MOSFETs
• For PowIRstage ICs (IR3553), the entire integrated module must be replaced

Found In These Miners

• Antminer S19 Series — TPS53647 (12 domains)
• Antminer S19 XP — TPS53647 (12 domains)
• Antminer S21 — MP2943 (12 domains)
• Whatsminer M50 — IR3553 (10 domains)
• Whatsminer M30S — IR3553 (10 domains)

Related Pages

• Voltage Regulators Overview
• LDO Regulators
• MOSFETs in Mining Hardware
• Capacitors in Mining Hardware
• Voltage Domains & Regulators
• Power Delivery Systems