Linear Technology has announced a high speed synchronous mosfet driver designed to drive upper and lower power N channel mosfets in a synchronous rectified converter topology.
According to Linear, the LTC4449 driver, combined with one of its dc/dc controllers and power FETs, forms 'a complete high efficiency synchronous regulator' that can be used as a step down or step up dc/dc converter. The LTC4449 drives both upper and lower mosfet gates over a range of 4 to 6.5V and operates from a supply voltage up to 38V. The driver can sink up to 4.5A and source up to 3.2A, making it suitable for driving high gate capacitance and high current mosfets. Linear says it can also drive multiple mosfets in parallel for higher current applications. The 8ns rise time, 7ns fall time of the top mosfet and 7ns rise time, 4ns fall time of the bottom mosfet, when driving a 3,000pF load, are designed to minimise switching losses. Adaptive shoot through protection is integrated to prevent the upper and lower mosfets from conducting simultaneously while minimising dead time. The LTC4449 features a 3 state pulse with modulation input for power stage control and shutdown that is compatible with all multiphase controllers employing a 3 state output feature. In addition, the LTC4449 has a separate supply for the input logic to match the signal swing of the controller ic, as well as an undervoltage lockout circuit on both the driver and logic supplies.