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LTC1876 - High Efficiency, 2-Phase, Dual Synchronous Step-Down Switching Controller and Step-Up Regulator

The LTC1876 is a high performance triple output switching regulator. It incorporates a dual step-down switching controller that drives all N-channel synchronous power MOSFET stages. A step-up regulator with an internal 1A, 36V switch provides the third output.

The step-down controllers minimize power loss and noise by operating the output stage of each controller out of phase. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. A RUN/SS pin for each controller provides both soft-start and an optional timed, short-circuit shutdown that can be configured to latch offone or both controllers. Current foldback provides additional short-circuit protection. In an overvoltage condition, the bottom MOSFET is latched on until VOUT returns to normal. The FCB pin can be used to inhibit Burst Mode operation or to enable regulation of a secondary output voltage.

The step-up regulator operates at 1.2MHz, allowing the use of tiny low cost capacitors and inductors. In addition,its internal 1A switch allows high current outputs to be generated. Its current mode control scheme provides excellent line and load regulation.

Features Step-Down Controller Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise Power Good Output Voltage Indicator OPTI-LOOP™ Compensation Minimizes COUT DC Programmed Fixed Frequency 150kHz to 300kHz Wide VIN Range: 3.5V to 36V Operation Very Low Dropout Operation: 99% Duty Cycle Adjustable Soft-Start Current Ramping Latched Short-Circuit Shutdown with Defeat Option Remote Output Voltage Sense and OV Protection 5V and 3.3V Standby Regulators Selectable Const. Freq. or Burst Mode™ Operation Step-Up Regulator High Operating Switching Frequency of 1.2MHz Low Internal VCESAT Switch: 400mV @ 1A, VIN = 3V Wide VIN Range: 2.6V to 16V Operation High Output Voltage: Up to 34V Typical Application

Applications 3.3V Input Step-Down Converter Notebook and Palmtop Computers, PDAs Battery-Operated Digital Devices Packaging

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