Analog Devices Inc./Maxim Integrated

The LT1533 is a new class of switching regulator designed to reduce conducted and radiated electromagnetic interference (EMI). Ultralow noise and EMI are achieved by providing user control of the output switch slew rates. Voltage and current slew rates can be independently programmed to optimize switcher harmonic content versus efficiency. The LT1533 can reduce high frequency harmonic power by as much as 40dB with only minor losses in efficiency.The LT1533 utilizes a dual output switch current mode architecture optimized for low noise topologies. The IC includes two 1A power switches along with 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 cycle by cycle current limit protection, undervoltage lockout and thermal shutdown.Low minimum supply voltage and low supply current during shutdown make the LT1533 well suited for portable applications. The part may also be forced into a 50% duty cycle mode for unregulated applications. The LT1533 is available in the 16-pin narrow SO package.ApplicationsPrecision Instrumentation SystemsIsolated Supplies for Industrial AutomationMedical InstrumentsWireless CommunicationsSingle Board Data Acquisition Systems

The LT1537 is a three-driver, five-receiver RS232 transceiver, pin compatible with the LT1137A, offering performance improvements and two shutdown modes. The LT1537µs charge pump is designed for extended compliance and can deliver over 35mA of load current. Supply current is typically 8mA, competitive with similar CMOS devices. An advanced driver output stage operates up to 250kbaud while driving heavy capacitive loads.The LT1537 is fully compliant with all RS232 specifications. Special bipolar construction techniques protect the drivers and receivers beyond the fault conditions stipulated for RS232. Driver outputs and receiver inputs can be shorted to ±25V without damaging the device or the power supply generator. In addition, the RS232 I/O pins are resilient to multiple ±5kV ESD strikes.The transceiver has two shutdown modes. One mode disables the drivers and the charge pump, the other shuts down all circuitry. While shut down, the drivers and receivers assume high impedance output states.ApplicationsNotebook ComputersPalmtop Computers

The LT1573 is a regulator driver IC designed to provide a low cost solution for applications requiring high current, low dropout and fast transient response. When combined with an external PNP power transistor, this device provides load current up to 5A with dropout voltages as low as 0.35V. The LT1573 circuitry is designed for extremely fast transient response. This greatly reduces bulk storage capacitance when the regulator is used in applications with fast, high current load transients.To keep cost and complexity low, the LT1573 uses a new time-delayed latching overcurrent protection technique that requires no external current sense resistor. Base drive is limited for instantaneous protection, and a time-delayed latch protects the regulator from continuous short circuits.The LT1573 is available as an adjustable regulator with an output range of 1.27V to 6.8V and with fixed output voltages of 2.5V, 2.8V and 3.3V. Output accuracy is better than 1% to meet the critical regulation requirement of fast microprocessors. A special 8-pin, fused-lead surface mount package is used to minimize regulator footprint and provide adequate heat sinking.Applications3.3V to 2.5V RegulatorMicroprocessor Power SourcePost Regulator for Switching SuppliesHigh Efficiency Linear RegulatorsUltralow Dropout RegulatorsLow Voltage Linear Regulators

The LT1576 is a 200kHz monolithic buck mode switching regulator. A 1.5A switch is included on the die along with all the necessary oscillator, control and logic circuitry. The topology is current mode for fast transient response and good loop stability. The LT1576 is a modified version of the industry standard LT1376 optimized for noise sensitive applications.In addition, the reference voltage has been lowered to allow the device to produce output voltages down to 1.2V. Quiescent current has been reduced by a factor of two. Switch on resistance has been reduced by 30%. Switch transition times have been slowed to reduce EMI generation. The oscillator frequency has been reduced to 200kHz to maintain high efficiency over a wide output current range.The pinout has been changed to improve PC layout by allowing the high current high frequency switching circuitry to be easily isolated from low current noise sensitive control circuitry. The new SO-8 package includes a fused ground lead which significantly reduces the thermal resistance of the device to extend the ambient operating temperature range. There is an optional function of shutdown or synchronization. Standard surface mount external parts can be used including the inductor and capacitors.ApplicationsPortable ComputersBattery-Powered SystemsBattery ChargerDistributed Power