As switch mode regulators gain popularity, classic linear regulators continue to hold their ground in certain applications, particularly when strict EMC regulations or low power requirements are involved. One such linear regulator is the STMicroelectronics L78L05ACD13TR, a derivative of the well-established LM78xx family. In this article, we will explore its features and discuss alternative options that offer improved specifications.  

Simplified Design:

The L78L05ACD13TR stands out for its simplicity, as demonstrated in the figure, requiring only two MLCC or other type capacitors for operation. While it is a reliable choice, it's important to note that alternative options exist, albeit at a higher cost.  

L78L05ACD13TR linear regulator circuits are very simple

Reducing Quiescent Current:

Quiescent current, which powers the linear regulator itself, is an important consideration. The L78L05ACD13TR has a quiescent current of 6mA. For applications requiring ultra-low quiescent current, the Analog Devices ADP3301ARZ-5 is worth considering, as it achieves a mere one micro-ampere in shut-down mode (see figure). Microchip's MIC5283-5.0YML-TR provides a quiescent current of 8uA, offering a balance between cost and performance, with a wider input voltage range than the ADP3301.  

The shut-down feature makes hibernating the auxiliary power supply easier if an ADP3301 type regulator is used

Heat Dissipation Considerations:

Linear regulators convert excess energy into heat, and caution must be exercised, especially when dealing with high input voltages. The L78L05ACD13TR has a maximum input voltage of 30V, while the MIC5283-5.0YML-TR can tolerate up to 120V DC. It is important to remember that even small currents can generate significant heat when transforming high input voltages to lower output voltages.  

Enhanced Accuracy with the LD59030:

Another crucial factor in selecting linear regulators is voltage range tolerance. While the L78L05ACD13TR offers accuracy within specified limits (refer to the figure), the LD59030 provides an impressive output voltage tolerance of +/-1% (see figure).  

The shut-down feature makes hibernating the auxiliary power supply easier if an ADP3301 type regulator is used

This increased accuracy makes it a desirable alternative for applications that demand precise voltage regulation.  

The shut-down feature makes hibernating the auxiliary power supply easier if an ADP3301 type regulator is used

Conclusion

The L78L05ACD13TR remains a popular choice among engineers, thanks to its affordability and availability from various semiconductor manufacturers. However, advancements in semiconductor manufacturing have introduced alternative options that offer significant improvements in capabilities at a slightly higher cost. By exploring alternatives such as the ADP3301ARZ-5, MIC5283-5.0YML-TR, and LD59030, engineers can find solutions that better suit their specific requirements. It is essential to strike a balance between cost, performance, and accuracy to achieve optimal results in linear regulator applications.