LT1123CST#TRPBF

Overview

The LT1123CST#TRPBF is a low dropout regulator driver designed for use with discrete PNP power transistors to create cost-effective regulators. It features a fixed 5V output trimmed to ±1% and operates with a quiescent current of 700µA. The device provides line regulation of 1mV and load regulation of 5mV. It guarantees an output current capability of up to 4A when paired with the specified MJE1123 pass transistor, achieving dropout voltages below 0.75V. The unit includes thermal limiting protection and is housed in a surface-mount SOT-223 package.

Feature Summary

• Integrated bandgap reference and error amplifier for precise voltage control
• Foldback drive current limits base drive during short-circuit conditions
• Thermal limit circuit protects both the driver and external pass transistor
• Drive pin allows series resistor insertion to minimize internal power dissipation

Applications

• Battery backup systems requiring stable 5V rails
• Lead-acid battery charging circuits
• Gel cell power supplies
• Low dropout regulator designs utilizing discrete PNP pass elements

Procurement Notes

Verify that the specific suffix TRPBF corresponds to the tape and reel packaging format required for automated assembly processes. Confirm that the ST package designation aligns with the intended surface mount footprint on the printed circuit board. Ensure the component meets RoHS compliance standards as indicated by the manufacturer documentation before finalizing procurement orders.

Selection Notes

Select this component when designing a regulator circuit that requires high output currents exceeding standard integrated LDO capabilities while maintaining low dropout characteristics. It is suitable for applications where minimizing component count and cost is critical compared to using fully integrated switching or linear solutions. Consider the thermal management requirements for both the driver and the external PNP transistor during selection.

Part Context

This part belongs to the LT1123 family of low dropout regulator drivers manufactured by Analog Devices Inc. It serves as a specialized interface between a feedback network and a high-power discrete transistor. Unlike monolithic regulators, this driver offloads the power handling to an external component, allowing for flexible output current ratings based on the selected pass transistor.

Replacement Considerations

LT1123CZ