Features

• Constant 500kHz Switching Frequency
• Easily Synchronizable
• Uses All Surface Mount Components
• Inductor Size Reduced to 5µH
• Saturating Switch Design: 0.4 ohms
• Effective Supply Current: 2.5mA
• Shutdown Current: 20µA
• Cycle-by-Cycle Current Limiting

Typical Application

Description

The LT1375/LT1376 are 500kHz monolithic buck mode switching regulators. A 1.5A switch is included on the die along with all the necessary oscillator, control and logic circuitry. High switching frequency allows a considerable reduction in the size of external components. The topology is current mode for fast transient response and good loop stability. Both fixed output voltage and adjustable parts are available.

A special high speed bipolar process and new design techniques achieve high efficiency at high switching frequency. Efficiency is maintained over a wide output current range by using the output to bias the circuitry and by utilizing a supply boost capacitor to saturate the power switch. A shutdown signal will reduce supply current to 20µA on both parts. The LT1375 can be externally synchronized from 580kHz to 900kHz with logic level inputs.

The LT1375/LT1376 fit into standard 8-pin PDIP and SO packages, as well as a fused lead 16-pin SO with much lower thermal resistance. Full cycle-by-cycle short-circuit protection and thermal shutdown are provided. Standard surface mount external parts are used, including the inductor and capacitors.

For low input voltage applications with 3.3V output, see LT1507. This is a functionally identical part that can operate with input voltages between 4.5V and 12V.