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LT1738 - Slew Rate Controlled Ultralow Noise DC/DC Controller

The LT1738 is a switching regulator controller designed to lower conducted and radiated electromagnetic interference (EMI). Ultralow noise and EMI are achieved by controlling the voltage and current slew rates of an exter-nal N-channel MOSFET switch. Current and voltage slew rates can be independently set to optimize harmonic content of the switching waveforms vs efficiency. The LT1738 can reduce high frequency harmonic power by as much as 40dB with only minor losses in efficiency.

The LT1738 utilizes a current mode architecture optimized for single switch topologies such as boost, flyback and Cuk. The IC includes gate drive and all necessary oscillator, control and protection circuitry. Unique error amp circuitry can regulate both positive and negative voltages. The internal oscillator may be synchronized to an external clock for more accurate placement of switching harmonics.

Protection features include gate drive lockout for low VIN, soft-start, output current limit, short-circuit current limit-ing, gate drive overvoltage clamp and input supply undervoltage lockout.

Features Greatly Reduced Conducted and Radiated EMI Low Switching Harmonic Content Independent Control of Output Switch Voltage and Current Slew Rates Greatly Reduced Need for External Filters Single N-Channel MOSFET Driver 20kHz to 250kHz Oscillator Frequency Easily Synchronized to External Clock Regulates Positive and Negative Voltages Easier Layout Than with Conventional Switchers Typical Application

Applications Power Supplies for Noise Sensitive Communication Equipment EMI Compliant Offline Power Supplies Precision Instrumentation Systems Isolated Supplies for Industrial Automation Medical Instruments Data Acquisition Systems Packaging

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