Power Electronics

DC-DC Controller

Linear Technology Corp.’s new LTC3703 is a 100-V, 95% efficient dc-dc step-down synchronous controller for simpler, lower cost and more efficient high-input voltage power supplies. The LTC3703 eliminates the need for a transformer and a current sense resistor. This single-inductor design not only withstands input transients up to 100 V, but also reduces the effect of input supply transients on the output with its patented line feed forward compensation.

The LTC3703's strong onboard 1-Ω gate drivers minimize switching transient losses associated with driving MOSFETs at high frequency. To optimize the size-cost ratio of inductors, MOSFETs and capacitors, the switching frequency is resistor-adjustable from 100 kHz to 600 kHz. The total solution cost of a LTC3703 power supply design is less than dc-dc bricks with comparable power levels. Applications include conversion of 36-V to 72-V backplane power to 12-V or 5-V intermediate supplies in telecom and servers, as well as power supplies in automotive and industrial systems susceptible to 90-V surges.

The LTC3703 drives N-channel MOSFETs synchronously to achieve high efficiency. Its 0.8-V reference voltage is±1% accurate. The adjustable soft-start guarantees safe start-up by eliminating overshoots. The LTC3703's high bandwidth (25-MHz) error amplifier and patented loop compensation provide very fast line and load transient responses that are superior to flyback topologies and existing high voltage dc-dc regulators. Moreover, current limit is user programmable with an external resistor.

For more information, visit www.linear.com.

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