Multi-topology regulator for non-isolated and isolated rails
The Analog Devices MAX629ESA+T is a current-mode PWM switching regulator that can be configured as a boost, flyback, or SEPIC converter. It delivers a single adjustable output up to ±28 V from an input of 2.7 V to 5.5 V, with a 500 mA switch current limit. The 300 kHz switching frequency keeps external inductor and capacitor sizes moderate for board-space-constrained designs. No synchronous rectifier is used, so the external diode selection matters for efficiency at higher output currents. Typical applications include LCD bias supplies, battery-powered equipment, and multi-output rails where a single inductor or coupled-winding transformer generates a positive or negative voltage.
Output voltage range and topology flexibility
The output is adjustable from ±0.8 V up to ±28 V, covering both positive and negative rail generation from a single IC. The SEPIC topology is particularly useful when the output voltage can be above, below, or equal to the input — a common requirement in battery-powered systems where the cell voltage drops below the regulated rail. Flyback mode adds isolation with a coupled inductor, though the IC itself does not provide isolation; the transformer turns ratio and feedback network set the output. This flexibility means one BOM line can serve multiple designs by changing only the external passives and transformer.
Surface-mount 8-SOIC package (0.154" body width, 3.90 mm). Standard SOIC-8 footprint; no thermal pad — junction-to-ambient thermal performance depends on copper area on the PCB. For 500 mA switch current in boost or SEPIC mode, ensure adequate ground-plane copper for heat spreading.