Buck Converter Withstands 40-V Transients

Linear Technology’s LT3505 is a current-mode PWM step-down dc-dc converter with an internal 1.75-A power switch, packaged in an 8-lead 3-mm x 3-mm DFN package. Its wide input range of 3.6 V to 36 V and capability to withstand 40-V transients makes the LT3505 ideal for regulating power from a wide variety of sources, including automotive batteries. For automotive applications, the LT3505's minimum input voltage of 3.6 V enables it to operate with <4 V inputs, paramount for meeting automotive "cold crank" requirements. Similarly, its 40-V input capability enables it to withstand transients found in load-dump conditions. Its 200-kHz to 3-MHz switching frequency is user programmable.

The LT3505's low VCESAT (350 mV at 1 A) internal switch offers efficiencies of over 90%, maximizing battery run-time. Its internal reference enables output voltages as low as 0.78 V. Internal cycle-by-cycle current limiting provides protection against shorted outputs while soft-start eliminates input current surge during start-up. The low current (<2 μA) shutdown provides easy power management in battery-powered systems.

The LT3505EDD is available now in a thermally enhanced 3-mm x 3-mm DFN-8 package. A higher temperature grade "I" version, the LT3505IDD, is also available. Pricing starts at $2.40 each and $2.88 each, respectively, for 1000-piece quantities.