ELECTRONICS: Linear Technology Corp. introduced the LTC3890/-1, a high voltage dual output synchronous step-down dc/dc controller that draws only 50µA when one output is active and 60µA when both outputs are enabled. With both outputs shut down, the LTC3890/-1 draws a mere 14µA. The 4 to 60V input supply range is designed to protect against high voltage transients, continue operation during automotive cold crank and cover a broad range of input sources and battery chemistries. Each output can be set from 0.8 to 24V at output currents up to 20A with efficiencies as high as 95 percent, making it well suited for 12 or 24V automotive, heavy equipment, industrial control, robotics and telecom applications.
The LTC3890/-1 has powerful 1.1Ω on-chip MOSFET gate drivers. It operates with a selectable fixed frequency between 50 and 900kHz, and can be synchronized to an external clock from 75 to 850kHz with its phased-locked loop (PLL). The user can select from continuous operation, pulse skipping and low ripple Burst Mode® operation during light loads. The LTC3890/-1’s 2-phase operation reduces input filtering and capacitance requirements. Its current mode architecture provides easy loop compensation, fast transient response and excellent line regulation. Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) for the highest efficiency or by using an optional sense resistor. Current foldback limits MOSFET heat dissipation during overload conditions. The device is available in two versions; the LTC3890 is the fully featured part with functions including a clock out, clock phase modulation, two separate power good outputs and adjustable current limit.
The LTC3890 is available in a 32-lead 5mm x 5mm QFN package and the LTC3890-1 is housed in a 28-pin SSOP package. Pricing starts at $4.76 each in 1,000-piece quantities.
In this new Design News feature, "How it Works," we’re starting off by examining the inner workings of the electronic cigarette. While e-cigarettes seemed like a gimmick just two or three years ago, they’re catching fire -- so to speak. Sales topped $1 billion last year and are set to hit $10 billion by 2017. Cigarette companies are fighting back by buying up e-cigarette manufacturers.
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