LD3985J33R

Overview

The LD3985J33R is a low-dropout linear voltage regulator manufactured by STMicroelectronics, designed for battery-powered applications. It provides a fixed 3.3V output with a maximum load current of 150mA. The device operates within an input voltage range of 2.5V to 6V and features ultra-low quiescent current, typically 85µA at no load and 170µA at full load. It includes logic-controlled shutdown functionality to minimize power consumption in standby modes. The regulator is stable with low ESR ceramic capacitors and offers high power supply rejection ratios of 60dB at 1kHz and 50dB at 10kHz.

Feature Summary

• Ultra-low dropout voltage performance ensures efficient operation even when the input voltage approaches the output level.
• Logic-controlled electronic shutdown function allows for significant power savings by placing the device in a low-current standby mode.
• Designed for stability with low equivalent series resistance (ESR) ceramic capacitors, simplifying circuit design.

Applications

• Mobile phones and similar battery-powered wireless systems
• Low power portable electronic devices requiring extended battery life
• Local regulators in battery-operated circuits needing shutdown control

Procurement Notes

Verify the specific suffix 'J' against official STMicroelectronics documentation to confirm package type and tape/reel specifications, as distributor listings may vary. Ensure compatibility with required output capacitance values for stability. Confirm RoHS compliance status for your region's regulatory requirements before finalizing procurement.

Selection Notes

Select this component for designs prioritizing low quiescent current and compact size in battery-operated environments. It is suitable where input voltages remain between 2.5V and 6V. Consider the 150mA output limit and thermal dissipation capabilities relative to the expected load current and ambient temperature conditions during system integration.

Part Context

The LD3985 series belongs to STMicroelectronics' family of ultra-low drop-out, low-noise BiCMOS voltage regulators. These components are engineered for low-power applications, offering high power supply rejection and fast turn-on times. The series supports various fixed output voltages and is optimized for use with small ceramic capacitors, making it ideal for space-constrained mobile and wireless devices.

Replacement Considerations

Check for direct pin-compatible alternatives within the LD3985 family or other ST LDOs with similar electrical characteristics. Verify that any substitute maintains the same output voltage, current capability, and shutdown logic compatibility. Cross-reference datasheets to ensure equivalent PSRR and quiescent current performance for the target application.