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High-speed MOSFET driver bucks or boosts efficiently

Posted: 25 Mar 2008 ?? ?Print Version ?Bookmark and Share

Keywords:high speed synchronous MOSFET driver? N-Channel MOSFETs? synchronous rectified converter topologies?

A high-speed synchronous MOSFET driver designed to drive upper and lower power n-channel MOSFETs in synchronous rectified converter topologies has been introduced by Linear Technology Corp. The LTC4443/-1 driver, combined with power MOSFETs and one of Linear Technology's many DC/DC controllers, forms a complete high efficiency synchronous regulator that can be used as a step-down or step-up DC/DC converter.

Minimizing losses
It can sink up to 5A and source up to 2.4A, making it suitable for driving high gate capacitance and high current MOSFETs. It can also drive multiple MOSFETs in parallel for higher current applications. Its fast 12ns rise time and 8nS fall time when driving a 3,000 pF load minimize switching losses. Adaptive shoot-through protection is integrated to prevent both the upper and lower MOSFETs from conducting simultaneously and to minimize dead time. An integrated bootstrap Schottky diode is incorporated which simplifies the circuit.

The LTC4443/-1 has a 3-state pulse-width modulator input for power stage shut-down that is compatible with all multi-phase controllers employing a 3-state output feature. It also has a separate supply for the input logic to match the signal swing of the controller IC and an undervoltage lockout circuit on both the driver and logic supplies. Furthermore, this part drives both upper and lower MOSFET gates over a range of 6V to 9.5V and operates up to a 38V supply voltage. The -1 version has a higher VCC undervoltage lockout of 6.2V instead of 3.2V, intended to drive standard 5V logic N-Channel MOSFETs.

The LTC4443EDD and LTC4443EDD-1 are offered in 3mm x 3mm DFN-12 packages with prices starting at $1.35 for 1000-piece quantities. The LTC4443IDD and LTC4443IDD-1, tested and guaranteed to operate from -40C to 85C operating temperature range are priced at $1.50 in 1,000-piece quantities.

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