L78M09CDT

The L78M09CDT is a fixed-output voltage regulator from STMicroelectronics, providing a stable +9V DC output at up to 500mA. It’s part of the L78Mxx series of linear regulators, featuring thermal overload protection, short-circuit protection, and safe operating area (SOA) control.
Key Features:
- Input Voltage Range: Up to 35V
- Output Voltage: Fixed 9V (±4% tolerance)
- Output Current: 500mA max
- Package: TO-252 (DPAK) for efficient heat dissipation
- Low Dropout Voltage: Suitable for moderate input-output differentials
Applications:
- Power supplies for microcontrollers, sensors, and small electronics
- Voltage stabilization in automotive, industrial, and consumer devices
Advantages:
- Simple to use (requires minimal external components)
- Built-in protections enhance reliability
Limitations:
- Linear regulators dissipate excess power as heat, reducing efficiency at high input-output differentials.
For higher currents or better efficiency, switching regulators may be preferred. Always refer to the datasheet for detailed specifications.

Equivalent products to the L78M09CDT (9V, 500mA linear voltage regulator) include:
- LM7809 (TO-220, TO-92)
- UA7809 (TO-220)
- MC7809 (TO-220)
- KA7809 (TO-220)
- L78M09ABDT (SOT-223, STMicroelectronics)
These are fixed 9V regulators with similar specs. Check pinout and package compatibility before substitution.

The L78M09CDT is a 9V, 500mA linear voltage regulator with the following key features:
- Output Voltage: Fixed 9V (±4% tolerance).
- Output Current: Up to 500mA.
- Input Voltage Range: Up to 35V (recommended ≥11V for stable 9V output).
- Low Dropout Voltage: ~2V (typical).
- Protections: Thermal shutdown, short-circuit, and overcurrent protection.
- Package: TO-252 (DPAK), surface-mount.
- Operating Temperature: -40°C to +125°C.
- Low Quiescent Current: ~5mA (typical).
Suitable for low-power applications requiring stable 9V supply, such as consumer electronics and industrial systems. Requires minimal external components (input/output capacitors).

The L78M09CDT is a 3-pin positive voltage regulator that provides a fixed +9V output.
Pin Functions:
1. Input (Pin 1): Connects to the unregulated DC input voltage (up to 35V).
2. Ground (Pin 2): Common ground reference.
3. Output (Pin 3): Delivers a stable +9V output (up to 500mA current).
This regulator includes built-in overcurrent protection, thermal shutdown, and short-circuit protection. It is commonly used in low-power applications requiring a stable 9V supply.
Package: TO-252 (DPAK).

The L78M09CDT is a 9V, 500mA linear voltage regulator. Its key application areas include:
- Consumer Electronics: Powering microcontrollers, sensors, and small circuits in devices like toys, audio equipment, and home appliances.
- Industrial Systems: Providing stable voltage for control modules, PLCs, and instrumentation.
- Automotive Electronics: Supporting infotainment systems, dashboards, and low-power peripherals (non-critical functions).
- Embedded Systems: Used in DIY projects, Arduino, and Raspberry Pi add-ons for reliable voltage regulation.
It’s ideal for low-to-medium power applications requiring a fixed 9V supply with thermal and short-circuit protection.