LT1521IS8-3.3

Overview

The LT1521IS8-3.3 is a micropower low dropout regulator with shutdown, manufactured by Analog Devices Inc. in an 8-lead plastic SO package. It provides a fixed 3.3V output at up to 300mA load current with a typical dropout voltage of 0.5V. The device features a quiescent current of 12µA and reduces to 6µA in shutdown mode. It operates within an industrial temperature range of -40°C to +125°C and includes reverse battery protection without requiring external diodes.

Feature Summary

• Micropower operation with controlled quiescent current that remains stable during dropout conditions
• Integrated shutdown pin for power management, reducing standby consumption significantly
• Reverse input and output protection capabilities suitable for backup power configurations
• Stable with small ceramic output capacitors, enhancing manufacturability

Applications

• Battery-powered systems requiring extended operational life
• Backup power situations where output must be held high while input is low or reversed
• Post-regulation for switching supplies

Procurement Notes

Verify the specific suffix IS8 confirms the industrial temperature grade (-40°C to +125°C) and SOIC-8 package. Confirm RoHS compliance status as datasheets may vary by revision. Check for obsolescence notices from Analog Devices, as older Linear Technology parts may have limited availability or require alternative sourcing strategies.

Selection Notes

Select this component when a fixed 3.3V rail is needed with minimal static power draw. Ensure the input voltage stays above 4.3V to maintain regulation under full load. Verify thermal constraints based on PCB copper area, as junction temperature limits power dissipation. Consider the sense pin connection for Kelvin sensing if trace resistance impacts accuracy.

Part Context

This part belongs to the LT1521 series of low dropout regulators designed for battery applications. It shares architectural similarities with the LT1121 but offers higher current capability. The series includes adjustable and fixed voltage variants in SOT-223 and SO packages, targeting portable electronics and industrial control systems.

Replacement Considerations

LT1521IS8-3#TR: Identical regulator with a fixed 3V output instead of 3.3V.

FAQ

How does the LT1521 handle reverse battery connections?

The device withstands reverse voltages on the input pin up to 20V. It acts like a diode in series with the input, preventing reverse current flow into the regulator and protecting both the device and the load.

What is the minimum required output capacitance?

A minimum output capacitor of 1.5µF is required to prevent oscillations. Larger values improve transient response for larger load current changes.