onsemi MC7805ABD2TR4G 5V Linear Voltage Regulator: Datasheet, Pinout, and Application Circuits
The onsemi MC7805ABD2TR4G is a classic and reliable positive voltage regulator integrated circuit (IC) belonging to the renowned 78xx series. It is designed to provide a fixed +5V DC output with a maximum current of 1A, making it a fundamental component in countless electronic devices requiring a stable, noise-free power rail from an unregulated input source.
This device is packaged in the D2PAK (TO-263) surface-mount package, which offers an excellent balance between compact size and efficient power dissipation. The "AB" designation indicates it meets onsemi's higher performance standards, including tighter voltage tolerance and improved specifications over the standard version.
Datasheet Overview: Key Specifications
Consulting the official datasheet is critical for any design. Key absolute maximum ratings and operational parameters include:
Input Voltage (VI): Up to 35V (typically designed for 7V to 25V for optimal performance).
Output Voltage (VO): 4.8V to 5.2V (5V nominal).
Output Current (IO): Up to 1A (requires adequate heatsinking).
Line Regulation: 10 mV (Typ.)
Load Regulation: 15 mV (Typ.)
Dropout Voltage (Vd): 2V (Typ.) at IO = 1A, TJ = 25°C. This is the minimum required difference between input and output voltage for regulation.
Operating Junction Temperature (TJ): -40°C to +125°C.
Pinout Configuration
The pinout for the D2PAK package is straightforward:
1. INPUT: This pin receives the unregulated DC input voltage.
2. GROUND (COMMON): This pin is connected to the system common ground.
3. OUTPUT: This pin provides the regulated +5V output.
Application Circuits
The MC7805ABD2TR4G is simple to implement, requiring only a few external components for most applications.
1. Basic Regulation Circuit:
The most common application circuit provides a clean, stable 5V output. The input capacitor (CIN, typically 0.33μF) is used to bypass high-frequency AC noise and suppress any tendency of oscillation, especially if the regulator is located far from the power supply filter. The output capacitor (COUT, typically 0.1μF) improves the transient response—its ability to handle sudden changes in load current—and further reduces output noise.
2. Circuit with Enhanced Ripple Rejection:
For applications where the input DC supply has significant AC ripple (e.g., from a simple rectifier circuit), the regulator's ability to reject this ripple can be improved. Adding a bypass capacitor (e.g., 10μF) between the common (ground) pin and the actual system ground can dramatically increase the ripple rejection ratio, leading to an even cleaner output.
3. Current Boosting with an External Transistor:
When the load requirement exceeds the 1A capability of the MC7805, an external PNP power transistor can be added. The regulator sources base current to the transistor, which then handles the majority of the load current. This configuration allows the circuit to deliver several amperes of current while the 7805 itself continues to provide voltage regulation and short-circuit protection.
Heatsinking Considerations
Due to its linear operation, the MC7805 dissipates power as heat. The power dissipated (PD) is calculated as:
PD = (VIN - VOUT) IOUT
For example, with a 12V input and a 1A load, the regulator must dissipate (12V - 5V) 1A = 7W. The D2PAK package must be mounted on a sufficiently large PCB copper area or an external heatsink to keep the internal junction temperature within safe limits, preventing thermal shutdown.
ICGOODFIND Summary
The onsemi MC7805ABD2TR4G remains a cornerstone of power management design. Its robustness, simplicity, and reliability make it an ideal choice for powering microcontrollers, logic circuits, sensors, and other low-power digital ICs. While switching regulators offer higher efficiency, the 7805's key advantages are its very low output noise and minimal external component count, ensuring it will continue to be a popular solution for applications where efficiency is secondary to simplicity and a clean power supply.
Keywords: Linear Voltage Regulator, 5V Fixed Output, D2PAK Package, Onsemi, Application Circuit
