LD3985M33R

Overview

The LD3985M33R is a fixed-output low-dropout linear regulator from STMicroelectronics, providing a stable 3.3V output with a maximum current of 150mA. It operates within an input voltage range of 2.5V to 6V and features ultra-low dropout characteristics, maintaining regulation even at minimal voltage differentials. The device incorporates a logic-controlled shutdown function to minimize standby power consumption. Designed for compatibility with low ESR ceramic capacitors, it ensures stability in compact surface-mount SOT-23-5 packages while supporting operation across a wide temperature range.

Feature Summary

• Ultra-low dropout voltage performance enables efficient regulation with minimal headroom requirements
• Logic-controlled electronic shutdown allows precise power management and reduced standby consumption
• Compatible with low ESR ceramic output capacitors for simplified circuit design and stability

Applications

• Battery-powered wireless systems requiring extended operational life
• Mobile phones and portable information appliances
• Low-power local voltage regulation in embedded circuits

Procurement Notes

Verify the specific suffix 'M33' confirms the fixed 3.3V output variant and 'R' indicates the tape-and-reel packaging format. Confirm the SOT-23-5 package designation matches your board layout constraints. Ensure the component meets RoHS compliance standards required for your assembly process. Cross-reference the manufacturer part number against official distributor catalogs to avoid counterfeit or obsolete stock.

Selection Notes

Select this component when a fixed 3.3V rail is required with minimal quiescent current draw. The 150mA output capacity suits moderate load applications without excessive heat dissipation. Its compatibility with ceramic capacitors reduces board space compared to tantalum alternatives. The shutdown pin provides system-level power control capabilities not available in standard LDOs.

Part Context

This device belongs to the LD3985 series of BiCMOS voltage regulators designed for low-noise and low-power applications. The series offers various fixed output voltages and supports inputs up to 6V. It is engineered for mobile and battery-operated electronics where efficiency and size are critical constraints.

Replacement Considerations

Direct substitutes include other LD3985 variants with different fixed output voltages if the voltage level differs. Verify pinout compatibility before replacing with generic LDOs, as internal protection features may vary.