Dual-phase synchronous buck controller — key parametrics for the BOM
The LTC1628IG-SYNC#PBF is a dual-output, 2-phase synchronous buck controller from Analog Devices (Linear Technology heritage), operating at a fixed 220 kHz switching frequency and capable of up to 99.4% duty cycle. It drives external N-channel MOSFETs from a 3.5 V to 30 V supply rail, making it suitable for intermediate bus conversion or point-of-load regulation in telecom, industrial, and computing power chains.
What the specs mean for the power-stage decision
The 99.4% maximum duty cycle means the controller can run the top FET nearly fully on — useful when the input voltage is only marginally above the output target, as in a 3.3 V rail from a 3.5 V input. The 220 kHz switching frequency is on the lower side for a modern buck controller; it keeps switching losses in the external FETs modest, but requires larger output inductance and capacitance than a 500 kHz+ part. The trade-off is worth it when efficiency at light load matters more than board area. Synchronous rectification is built in — the controller drives both the high-side and low-side N-channel FETs, eliminating the Schottky catch diode's forward drop. This recovers the conduction loss that would otherwise be dissipated as heat in the diode, improving full-load efficiency by typically 3-5% over an asynchronous buck at the same output current. The control features include Enable, Frequency Control, Power Good, and Soft Start. The Frequency Control pin allows synchronizing to an external clock or setting the oscillator frequency with a resistor — useful when the switcher must avoid a sensitive band in the downstream load's noise spectrum. Soft Start ramps the output voltage on startup, preventing inrush current from tripping the upstream supply.
Package, temperature grade, and compliance
The supplier device package is 16-SSOP; the tube delivery is suitable for hand assembly or low-volume pick-and-place.