Power Electronics

New Products October 1

Dual-Output Synchronous DC-DC Controller IC

The LTC3858/-1 low-quiescent-current, two-phase dual-output synchronous step-down dc-dc controller from Linear Technology draws only 170 µA with one output active and 300 µA when both outputs are active. With both outputs shut, the device draws 8 µA to suit automotive and notebook PC applications.

The 4- to 38-V input-supply range protects against automotive wide-input voltage transients commonly found during load-dump and cold-crank conditions, and covers a broad range of battery chemistries. Each output can be set from 0.8 to 24 V at output currents to 20 A with efficiencies as high as 95%. The controller can power high-performance systems including navigation, audio, communications, and disk drives.

Featuring on-board MOSFET gate drivers, the device operates with an adjustable fixed frequency between 50 kHz and 900 kHz or can be synchronized to an external clock from 75 kHz to 850 kHz using its PLL. Users can select from continuous operation, pulse-skipping, and low-ripple Burst Mode® operation during light loads.

Two-phase operation reduces input capacitance requirements, and a current-mode architecture provides loop compensation and fast transient response. Both outputs have adjustable soft-start capability to control the turn-on time, and the output overload protection feature latches off the converter until the input voltage is recycled.

The LTC3858/-1 also features a tight ±1% reference-voltage accuracy over the operating temperature range of ?40° to 85°C. The LTC3858 is the fully featured version, with additional functions beyond the LTC3858-1 including a clock out, clock-phase modulation, two separate power-good signals, and adjustable current limit.

The LTC3858 comes in a 32-lead 5- × 5-mm QFN package, with the LTC3858-1 in offered in a 28-pin SSOP or 4- × 5-mm QFN-28. Pricing starts at $4.47 in 1,000-piece quantities.

Linear Technology
Milipitas, CA

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