The MAX256 is an integrated primary-side controller and H-bridge driver for isolated power-supply circuits. The device contains an on-board oscillator, protection circuitry and internal FET drivers to provide up to 3W of power to the primary winding of a transformer. The MAX256 can be operated using the internal program- mable oscillator or can be driven by an external clock for improved EMI performance. Regardless of the clock source being used, an internal flip-flop stage guaran- tees a fixed 50% duty cycle to prevent DC current flow in the transformer. The MAX256 operates from a single-supply voltage of +5V or +3.3V, and includes undervoltage lockout for controlled startup. The device prevents cross-conduc- tion of the H-bridge MOSFETs by implementing break- before-make switching. Thermal shutdown circuitry provides additional protection against damage due to overtemperature conditions. The MAX256 is available in the 8-pin thermally-enhanced SO package. The device is specified for the automotive (-40°C to +125°C) temperature range.