Features

• 1.5A Switch Current
• High Efficiency—Low Loss 0.2Ohms Switch
• Constant 200kHz Switching Frequency
• 4V to 15V Input VoltageRange
• Minimum Output: 1.21V
• Low Supply Current: 1.9mA
• Low Shutdown Current: 20µA
• Easily Synchronizable Up to 400kHz
• Cycle-by-Cycle Current Limit
• Reduced EMI Generation
• Low Thermal Resistance SO-8 Package
• Uses Small Low Value Inductors

Typical Application

Description

The LT1578 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 LT1578 is a modified version of the LT1507 that has been optimized for noise sensitive applications. It will operate over a 4V to 15V input range. 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 that significantly reduces the thermal resistance of the device to extend the ambient operating temperature range. Standard surface mount external parts can be used including the inductor and capacitors.