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.
Package and mounting
Surface-mount 8-SOIC package (0.154" body width, 3.90 mm). The supplier device package is also 8-SOIC. 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.