L78M09CP

Overview

The L78M09CP is a three-terminal positive linear voltage regulator from the STMicroelectronics L78MxxA series, housed in a TO-220FP package. It provides a fixed output voltage of 9V with a maximum continuous output current of 500mA. The device supports a DC input voltage up to 35V and operates within a junction temperature range of 0°C to 125°C for the AC grade. Key electrical characteristics include a typical quiescent current of 6mA, a dropout voltage of 2V at 350mA, and supply voltage rejection of 56dB at 120Hz. It features internal thermal overload protection, short-circuit protection, and output safe-area compensation.

Feature Summary

• Integrated thermal overload protection that shuts down the circuit during excessive power conditions
• Internal short-circuit protection limits maximum output current to prevent damage
• Output transistor safe-area protection reduces output current as voltage across the pass transistor increases

Applications

• Local on-card regulation to eliminate distribution problems associated with single-point regulation
• Power supplies requiring fixed 9V output with moderate current demands
• Battery-powered systems utilizing external components for adjustable voltage configurations

Procurement Notes

Verify the specific suffix (e.g., AB vs AC) against the required operating temperature range, as the datasheet distinguishes between -40°C to 125°C and 0°C to 125°C grades. Confirm the package type matches the TO-220FP footprint requirements for your PCB design. Ensure adequate heat sinking is provided if the application requires sustained operation near the 500mA limit to maintain thermal stability.

Selection Notes

Select this component when a fixed 9V output is needed with up to 500mA capability in a through-hole package. Consider the L78MxxAC grade if the application environment does not require sub-zero temperatures, as it offers a narrower but sufficient operational range. Evaluate thermal resistance values (RthJA of 50°C/W) to determine necessary heatsinking for high-differential voltage applications.

Part Context

This part belongs to the L78MxxA series of precision 500mA regulators available in multiple fixed output voltages including 5V, 6V, 8V, 10V, 12V, 15V, and 24V. The series is designed for wide-ranging applications where local regulation is preferred over centralized power distribution. It shares functional similarities with other three-terminal regulators but is distinguished by its specific current rating and integrated safety features.

Replacement Considerations

L78M09AB

FAQ

What is the maximum input voltage for the L78M09CP?

The maximum DC input voltage is 35V for output voltages ranging from 5V to 18V.

Does the L78M09CP require external capacitors for stability?

While often stable without them in low-current applications, an input bypass capacitor (0.33µF or larger) is recommended if connected via long wires or if the load capacitance is large.