L78L33ABD

Overview

The L78L33ABD is a three-terminal positive linear voltage regulator from the STMicroelectronics L78L series. It provides a fixed output voltage of 3.3 V with an output current capability up to 100 mA. The device features internal current limiting and thermal shutdown protection, ensuring robust operation under overload conditions. It operates within a junction temperature range of -40 °C to +125 °C. The maximum DC input voltage is rated at 30 V for this output voltage level. The component requires no external components for basic regulation and is available in surface-mount packages such as SO-8.

Feature Summary

• Internal current limiting and thermal shutdown protection prevent damage during overload conditions.
• Fixed 3.3 V output eliminates noise and distribution problems associated with single-point regulation.
• Capable of delivering up to 100 mA output current when adequate heat sinking is provided.
• Functions as a direct replacement for Zener diode and resistor combinations with improved performance.

Applications

• Local or on-card voltage regulation
• Replacement for Zener diode/resistor combinations
• Construction of high-current regulators using power pass elements

Procurement Notes

Verify that the ordering suffix 'D' corresponds to the specific package type required, typically indicating an SO-8 surface mount configuration. Confirm the 'AB' designation ensures the extended -40 °C to +125 °C operating temperature range. Ensure the application circuit includes appropriate input and output capacitors as specified in the datasheet test conditions for stable operation.

Selection Notes

Select this component when a fixed 3.3 V supply is needed with moderate current demands up to 100 mA. The wide operating temperature range makes it suitable for industrial environments. Consider the thermal resistance characteristics of the SO-8 package and ensure sufficient copper area on the PCB for effective heat dissipation to maintain reliable performance at higher ambient temperatures.

Part Context

This part belongs to the L78L series of three-terminal positive regulators manufactured by STMicroelectronics. The series offers various fixed output voltages including 3.3, 5, 6, 8, 9, 10, 12, 15, 18, and 24 V. The 'A' selection indicates a tighter ±4% output voltage tolerance compared to the standard ±8% option. The series is designed for general-purpose linear regulation applications requiring simple implementation and inherent protection features.

Replacement Considerations

Direct replacements include other L78L33 variants such as L78L33ACD (±8% tolerance) or L78L33ABZ (TO-92 package). Cross-series equivalents like the LM340T-3.3 may require verification of pinout compatibility and thermal performance differences.