MT3608

The MT3608 is a constant-frequency, current-mode step-up (boost) DC-DC converter intended for small, low-power applications. It operates over an input voltage range of 2V to 24V and provides an adjustable output voltage up to 28V. The device operates at a fixed 1.2MHz switching frequency, allowing the use of compact external inductors and capacitors. It integrates an 80mΩ internal power MOSFET with a 4A internal switch current limit and is available in a 6-pin SOT23-6 package.

A typical MT3608 boost converter requires an inductor, Schottky diode, input capacitor, output capacitor, and an external resistor divider to set the output voltage. The recommended inductor value is 4.7µH to 22µH. The datasheet recommends 22µF low-ESR ceramic capacitors (X5R or X7R) for both the input and output. A Schottky diode is recommended because of its low forward voltage drop and fast recovery, improving efficiency at the converter's 1.2MHz switching frequency. The output voltage is programmed using an external resistor divider referenced to the 0.6V feedback voltage.

The MT3608 uses a fixed-frequency, peak current-mode control architecture to regulate output voltage. It operates at a 1.2MHz switching frequency and automatically shifts to Pulse Frequency Modulation (PFM) mode under light-load conditions to improve efficiency. Typical quiescent current in PFM mode is 100–200µA, and the converter achieves up to 93% efficiency, depending on operating conditions and external component selection. Internal soft-start helps reduce inrush current during startup, while current limiting and thermal protection improve reliability during operation.

Good PCB layout is essential for reliable operation of the MT3608. The input and output capacitors should be placed close to the IC and connected to a solid ground plane to reduce noise. High-current traces should be kept short and wide, and the SW node area should be minimized to reduce switching noise. The feedback components should be placed close to the IC and routed away from noisy switching nodes to maintain stable output regulation. A solid ground plane also improves thermal performance and reduces electrical noise.

The MT3608 includes under-voltage lockout (UVLO), current limiting, thermal overload protection, and internal soft-start to improve reliability during startup and fault conditions. The datasheet specifies a typical thermal shutdown temperature of 155°C and a 4A internal switch current limit. In practical applications, overall performance depends on proper component selection, PCB layout, and adequate thermal management to ensure stable operation and high efficiency.