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Synchronous step-down switching regulators deliver 96% efficiency

The LT8610 and LT8611 from Linear Technology Corp. are 2.5 A, 42 V input capable synchronous step-down switching regulators. Synchronous rectification delivers efficiency as high as 96% while Burst Mode operation keeps quiescent current under 2.5 µA in no-load standby conditions. A 3.4 to 42 V input voltage range makes the parts well suited for automotive and industrial applications.

Internal 3.5 A switches can deliver up to 2.5 A of continuous output current to voltages as low as 0.97 V. The LT8611 includes all of the features of the LT8610, plus a built-in current sense amplifier with monitor and control pins, enabling accurate input or output current regulation and limiting. Following are more details on each model, plus links to data sheets:

LT8610
The LT8610 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 2.5 μA of quiescent current. Top and bottom power switches are included with all necessary circuitry to minimize the need for external components. Low ripple Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10 mVP-P. A SYNC pin allows synchronization to an external clock.

Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1-V threshold and can be used to program VIN undervoltage lockout or to shut down the LT8610 reducing the input supply current to 1 μA. A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up. The PG flag signals when VOUT is within ±9% of the programmed output voltage as well as fault conditions. The LT8610 is available in a small 16-lead MSOP package with exposed pad for low thermal resistance.

LT8611
The LT8611 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 2.5 μA of quiescent current. Top and bottom power switches are included with all necessary circuitry to minimize the need for external components. The built-in current sense amplifier with monitor and control pins allows accurate input or output current regulation and limiting. Low ripple Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10 mVP-P. A SYNC pin allows synchronization to an external clock.

Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1-V threshold and can be used to program VIN undervoltage lockout or to shut down the LT8611 reducing the input supply current to 1 μA. A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up. The PG flag signals when VOUT is within ±9% of the programmed output voltage as well as fault conditions. The LT8611 is available in a small 24-lead 3 × 5 mm QFN package with exposed pad for low thermal resistance.

For more information, contact Linear Technology Corp., 1630 McCarthy Blvd., Milpitas, CA 95035. Phone: (408) 432-1900.

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