Buck Converter (Step-Down DC-DC)
High-efficiency step-down switching converters for the heart of any modern power tree.
What is it?
A buck converter is a switching regulator that steps a higher input voltage down to a lower output with very high efficiency (typically 85-95%). Energy is transferred in pulses through an inductor, not dissipated as heat like in an LDO. Almost every modern system uses bucks as the main rail generators (12 V → 5 V, 5 V → 3.3 V, 3.3 V → 1.8 V, etc.).
When do you need it?
- Anywhere Vin > Vout and load current >300 mA.
- Battery-powered devices where every milliwatt of waste reduces runtime.
- Multi-rail systems generating processor / memory / IO voltages from a common bus.
- Automotive 12 V → 5 V / 3.3 V / 1.2 V conversion.
How to pick the right one
- VIN range
- Must span all input conditions including transients. 2.5-6 V (battery), 4.5-18 V (12 V rail), up to 60 V or higher for industrial.
- VOUT range
- Adjustable down to feedback reference (0.6 V typical) or fixed variants.
- IOUT (maximum continuous)
- 1 A / 2 A / 3 A / 5 A common. Add 20% margin for transients.
- Switching frequency
- Higher fSW = smaller inductor/cap but more switching loss. 500 kHz-2 MHz typical. >1.5 MHz allows tiny ceramic-only filters.
- Control scheme
- COT (Constant-On-Time) for fast transient response, voltage-mode for simplicity, current-mode for line-rejection.
- Synchronous vs Asynchronous
- Synchronous bucks integrate the freewheel diode as a MOSFET → higher efficiency, especially at light load.
What Magnias offers
Magnias buck converters cover 1 A to 8 A output and 1.95 V to 60 V input, in packages from CSP0.74×1.09-6L up to ESOP-8. About half use COT or adaptive COT control for fast transient response. Highlights: MI4018T Series (1.95-5.5 V, ultra-low quiescent current), MI2262G Series (2 A, 1.6 MHz), MI6028P Series (8 A, 4.5-24 V), MI2613B-S6 (4.5-60 V, 1 A), MI24493F-N22 (4.15-36 V, 3 A, AEC-Q100 qualified) and the MI5318A-TF4 controller for external MOSFETs. For multi-rail automotive camera power, see the MI8101B-N33 PMIC.