LDS3985M18R

Overview

The LDS3985M18R is a fixed-output linear voltage regulator manufactured by STMicroelectronics. It provides a fixed output voltage of 1.8 V with a maximum output current of 300 mA. The device operates from an input voltage range of 2.5 V to 6 V and features a typical dropout voltage of 400 µV. Key electrical parameters include a quiescent current of 150 µA, power supply rejection ratio (PSRR) of 55 dB at 1 kHz and 50 dB at 10 kHz, and an operating temperature range of -40°C to +125°C. It utilizes a TSOT-23-5 surface-mount package.

Feature Summary

• Ultra-low dropout voltage performance for efficient power regulation
• Logic-controlled electronic shutdown function to reduce standby power consumption
• Internal overcurrent and thermal limit protection mechanisms
• Stable operation with low ESR ceramic capacitors

Applications

• Battery-powered wireless systems
• Portable information appliances
• Mobile phones

Procurement Notes

Verify component authenticity through authorized distribution channels due to the availability of counterfeit parts in the market. Confirm that the received units match the specific LDS3985M18R marking and package type. Check for RoHS compliance documentation as required by regional regulations. Ensure storage conditions adhere to moisture sensitivity level guidelines to prevent package damage prior to soldering.

Selection Notes

Select this component when a fixed 1.8 V rail is required with moderate current demands up to 300 mA. The TSOT-23-5 package offers a compact footprint suitable for space-constrained designs. Consider the ultra-low dropout characteristic for applications where the input voltage closely approaches the output voltage. Verify that the load transient requirements are met by the external capacitor selection specified in the datasheet.

Part Context

This part belongs to the LDS3985 series of BiCMOS low-dropout regulators designed for low-power applications. The series offers various fixed output voltages ranging from 1.25 V to 5 V. The LDS3985 family is characterized by low noise and high PSRR, making it suitable for sensitive analog circuits in portable devices. The M18 suffix specifically denotes the 1.8 V fixed output variant.

Replacement Considerations

Direct pin-to-pin replacements within the same package may include other LDS3985 variants with different fixed output voltages, provided the system design accommodates the voltage change. Cross-referencing with similar 300 mA LDOs requires verification of dropout voltage, quiescent current, and stability criteria with compatible output capacitors.