Flyback controller for isolated and non-isolated offline supplies
The MAX5974EETE+T from Analog Devices is a current-mode flyback switching controller designed for offline and DC-DC converter applications. It operates from a 7V to 26V supply rail and supports a switching frequency range of 100kHz to 600kHz, set by an external resistor on the RT pin. The controller integrates control features including enable (EN), frequency control, soft-start, and synchronization (Sync), along with fault protection for current limiting, over-temperature, and short-circuit conditions. The 80% maximum duty cycle suits universal-input flyback designs typical in PoE-powered devices, auxiliary supplies, and industrial power converters. The part is rated for -40°C to +85°C ambient operation, covering most commercial and industrial environments.
Switching frequency range and transformer sizing
The 100kHz to 600kHz programmable switching frequency gives the designer flexibility to trade off transformer size against switching losses. At the lower end, 100kHz keeps core losses down in a physically larger magnetics; at 600kHz the transformer shrinks but gate-drive losses and snubber dissipation rise. The controller itself does not include an internal power switch, so the external MOSFET's gate charge and the transformer leakage inductance must be managed in the layout. The 16-TQFN (3x3mm) exposed-pad package helps thermal conduction from the controller die, but the main dissipation is in the external FET and output diode.
Active lifecycle — no LTB risk
ROHS3 compliant.