Onsemi MC7808BD2TR4G 8V 1A Positive Voltage Regulator LDO Datasheet and Application Circuit Design Guide
The Onsemi MC7808BD2TR4G is a widely used positive voltage regulator belonging to the popular 78xx series of linear regulators. It provides a fixed 8V output at currents up to 1A, making it suitable for a broad range of power management applications. This component is packaged in a D2PAK (TO-263) surface-mount package, designed for efficient power dissipation.
Key Electrical Characteristics and Features
The device is designed with internal current limiting, thermal shutdown protection, and safe-area compensation, making it highly resilient to overload conditions. A key advantage of this series is its simplicity of use; often, only two external capacitors are required for stable operation, simplifying circuit design and reducing board space.
Its typical dropout voltage is around 2V at 1A load. This means the input voltage must be maintained at least 2V above the 8V output to ensure regulation. For reliable performance, the recommended input voltage range is 10.5V to 25V. The regulator can deliver a peak output current of 2.2A under specific conditions, providing a good margin for transient loads.
Standard Application Circuit Design
A typical application circuit for the MC7808BD2TR4G is straightforward. The basic configuration requires only two capacitors:
Input Capacitor (C_IN): A 0.33μF ceramic or tantalum capacitor should be placed close to the input pin. This capacitor helps neutralize the effects of inductive wiring and improves circuit stability, especially when the regulator is located far from the power supply filter.
Output Capacitor (C_OUT): A 0.1μF ceramic capacitor is recommended at the output to improve transient response and stability. While the device is stable without it, this capacitor ensures optimal performance.
For applications with large variations in load current or temperature, a larger electrolytic capacitor (e.g., 10μF to 100μF) at the output can be added to further enhance stability and transient response.
Thermal Management Considerations
As a linear regulator, the MC7808BD2TR4G dissipates power as heat. The power dissipation (P_D) is calculated as:
P_D = (V_IN – V_OUT) × I_LOAD
For example, with an input of 12V and a full 1A load, the device would dissipate (12V – 8V) × 1A = 4 Watts. The D2PAK package has a junction-to-case thermal resistance (θ_JC) of 5°C/W and a junction-to-ambient (θ_JA) of 50°C/W. Proper heatsinking is critical to prevent the internal thermal protection circuit from shutting down the device. For high-power scenarios, the package should be mounted on a sufficient copper area on the PCB or an external heatsink to ensure the junction temperature remains below the maximum 125°C.
Typical Applications
Power supplies for microcontroller (MCU) and logic circuits requiring 8V.
Local regulation for specific modules within a larger system.
Constant voltage sources for sensors and analog circuitry.
Post-regulation after a switching pre-regulator to achieve low-noise outputs.
ICGOODFIND Summary
The Onsemi MC7808BD2TR4G is a robust and highly reliable linear voltage regulator ideal for applications requiring a stable 8V rail. Its key strengths lie in its simplicity, built-in protection features, and high current capability. Designers must pay close attention to input voltage requirements and, most importantly, thermal management to ensure optimal performance and long-term reliability. It remains a fundamental and cost-effective solution for linear power regulation.
Keywords: Positive Voltage Regulator, Thermal Management, Application Circuit, 1A Output Current, Dropout Voltage
