The LTC1267 series are dual synchronous step-down switching regulator controllers featuring automatic Burst ModeTM operation to maintain high efficiencies at low output currents. The LTC1267 is composed of two separate regulator blocks, each driving a pair of external complementary power MOSFETs at switching frequencies up to 400kHz. The LTC1267 uses a constant off-time currentmode architecture to provide constant ripple current in the inductor and provide excellent line and load transient response.