MAX17554/MAX17555 Step-Down DC/DC Converters

ADI's MAX17554 and MAX17555 are ultra small, high-efficiency, high voltage, synchronous step-down DC-DC converters with integrated MOSFETs operating over a wide input voltage range and delivering up to 50 mA of load current. The MAX17554 operates over a wide input voltage range from 10 V to 60 V, and the MAX17555 operates over a wide input voltage range from 4 V to 60 V.

The MAX17554 offers a converter solution with only three active pins, whereas the MAX17555 offers a flexible converter design in terms of EN/UV and HYST thresholds and active-low RESET features. The MAX17554A and MAX17555A and the MAX17554B and MAX17555B are fixed 3.3 V and 5 V output voltage devices, respectively. The MAX17554C and MAX17555C are adjustable output (0.8 V to 0.9 x V_IN) devices. The feedback voltage regulation accuracy of the converters over the -40°C to +125°C temperature range is ±1.5% for the MAX17554A and MAX17555A and the MAX17554B and MAX17555B, and ±1.25% for the MAX17554C and MAX17555C.

The devices feature a peak-current mode control architecture. During normal operation, at each rising edge of the clock, the high-side p-MOSFET turns on and remains on until either the appropriate or maximum duty cycle is reached or the peak current limit is detected. During the high-side p-MOSFET on-time, the inductor current ramps up. During the rest of the switching cycle or until the inductor current reaches zero, the high-side p-MOSFET remains off, the low-side n-MOSFET remains on, and the inductor current ramps down. The device features the discontinuous conduction mode (DCM), in which the negative inductor current is inhibited for higher light load efficiency. In DCM, the device operates at a fixed switching frequency until the minimum on-time is reached. If the load demand is less than the energy corresponding to the minimum on-time pulse, the converter skips pulses to maintain output voltage regulation.