The LT3509 dual-channel, step-down dc-dc converter has two internal 36-V, 1-A power switches and comes packaged in a 14-lead 3- by 4-mm package. Each channel of the current-mode pulse-width modulation (PWM) converter can deliver up to 700 mA of output current with efficiencies up to 88%. Device input ranges from 3.6 V to 36 V, with transient protection to 60 V.
These features make the LT3509 well suited for regulating power from a wide variety of sources, including unregulated wall transformers, 24-V industrial supplies, and automotive batteries. It can handle the sub 4-V inputs needed for automotive “cold crank” operation, and it can also withstand transients found in load-dump scenarios.
The converter’s 300-kHz to 2.2-MHz switching frequency is user programmable. It maximizes efficiency while using tiny, low-cost inductors and ceramic capacitors, resulting in low, predictable output ripple. The low VCESAT (320 mV at 0.9 A) of both internal switches offers efficiencies up to 88%, minimizing wasted heat.
An internal 0.80-V reference enables the sub 1-V output voltages required to power the latest generation of low-voltage DSPs and microcontrollers. Low-dropout internal switches allow duty cycles to reach 95%, while internal cycle-by-cycle current limit provides protection against shorted outputs. The low-current ( less than 9 µA) shutdown translates to extended runtime in battery-powered systems.
The LT3509EDE is available in a thermally enhanced 3- by 4-mm DFN-14 package. The LT3509EMSE comes in a thermally enhanced MSOP-16E package. Pricing starts at $2.95 and $3.05, respectively. Also available are industrial-temperature-grade versions, the LT3509IDE and LT3509IMSE, which are tested and guaranteed to operate from a –40°C to 125°C operating junction temperature. They cost $3.39 and $3.51, respectively. All versions are available from stock.
Linear Technology
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