L5991D

AC DC Converters, Offline Switchers Overview

The L5991D is a primary controller IC from STMicroelectronics, designed for offline or DC-DC power supply applications using fixed frequency current mode control. It supports Boost and Flyback topologies with a single output. The device operates within a supply voltage range of 7.6V to 20V and features a switching frequency up to 1 MHz. It provides an output current capability of 1.5 A and includes programmable soft start, IN/OUT synchronization, and standby functions. The component is housed in a 16-SOIC package and operates across a temperature range of -40°C to +150°C.

AC DC Converters, Offline Switchers Feature Summary

• Implements fixed frequency current mode PWM control for efficient power management.
• Includes programmable soft start and precise maximum duty cycle control.
• Features a standby function that reduces oscillator frequency under light load conditions to minimize power losses.
• Provides primary overcurrent fault detection with restart delay and pulse-by-pulse current limit.

AC DC Converters, Offline Switchers Applications

• Offline power supply implementations
• Flyback topology converters
• Boost converter designs
• Equipment requiring energy-saving compliance

AC DC Converters, Offline Switchers Procurement Notes

Verify the specific suffix (e.g., D vs AD) against the manufacturer's datasheet to confirm pinout and electrical tolerances. Ensure the selected package variant matches the PCB footprint requirements. Confirm humidity sensitivity level and storage conditions prior to assembly. Cross-reference the ordering code with official distributor catalogs to avoid substitution errors during procurement.

AC DC Converters, Offline Switchers Selection Notes

Select this component for applications requiring high efficiency at light loads due to its standby frequency reduction feature. Consider the 1 MHz switching frequency for compact magnetic design. Evaluate the SOIC-16 package constraints for thermal management. Verify input voltage ranges align with the 7.6V to 20V operating specification. Assess the need for external MOSFET drive capabilities given the 1A output drive strength.

AC DC Converters, Offline Switchers Part Context

The L5991D belongs to the L5991 series of switching controllers developed in BCD60II technology. It serves as a primary side controller for isolated and non-isolated power supplies. The series is optimized for flyback applications but supports boost topologies. It integrates protection features like UVLO and leading edge blanking, distinguishing it from basic PWM controllers by offering advanced power management functionalities.

AC DC Converters, Offline Switchers Replacement Considerations

L5991AD is a compatible variant within the same series. Verify pin compatibility and electrical parameter differences before substitution. Check datasheet revisions for any functional changes between the D and AD suffixes.