onsemi MCR106-8G SCR: Datasheet, Pinout, and Application Circuit Guide
The MCR106-8G from onsemi is a robust and reliable Silicon Controlled Rectifier (SCR) designed for a wide range of AC switching and control applications. This sensitive gate SCR is part of the popular MCR106 series, known for its high surge current capability and low cost. This guide provides a detailed overview of its datasheet, pinout, and a typical application circuit to help engineers effectively integrate this component into their designs.
Datasheet Overview and Key Specifications
The MCR106-8G is a plastic-encapsulated SCR in a TO-92 package, making it suitable for through-hole PCB mounting. Its key electrical characteristics make it ideal for industrial and consumer applications like motor controls, light dimmers, and power supplies.
Critical maximum ratings and electrical characteristics from the datasheet include:
Repetitive Peak Off-State Voltage (VDRM): 600 V
Gate Trigger Current (IGT): 200 µA (max) – This high sensitivity allows it to be triggered easily by low-current sources like logic circuits or sensors.
On-State Current (IT(RMS)): 4 A RMS
Non-Repetitive Peak Surge Current (ITSMM): 40 A (for one half sine wave at 60 Hz) – This high surge rating provides excellent overload protection against transient events.
Operating Junction Temperature (TJ): -40°C to +125°C
These specifications highlight the device's ability to handle significant power in a compact form factor while being triggered with minimal gate current.
Pinout Configuration
The MCR106-8G comes in a standard TO-92 package. When viewing the component with the flat side facing you and the leads pointing downward, the pinout from left to right is as follows:
1. Anode (A)
2. Gate (G)
3. Cathode (K)
Correct pin identification is crucial for the circuit to function properly and to prevent damage to the SCR during testing and operation.
Typical Application Circuit Guide
A common use for the MCR106-8G is in AC power control circuits, such as a simple half-wave AC switch for controlling a light bulb or a small motor. The basic circuit operation is as follows:
1. Circuit Setup: The Anode (A) is connected to the AC source (e.g., 120V AC line) through the load (e.g., a lamp). The Cathode (K) is connected to the neutral line of the AC source.
2. Triggering Mechanism: The Gate (G) is driven by a triggering circuit. This can be as simple as a pushbutton switch connected in series with a current-limiting resistor to a DC voltage source. The resistor value must be chosen to limit the gate current to a safe level, typically below the maximum peak gate current of 2A but above the minimum required to trigger (200 µA). More complex triggers using diacs, microcontrollers, or pulse transformers are also common.
3. Operation: When the anode is positive relative to the cathode and a sufficient positive gate current pulse is applied, the SCR turns ON and conducts current through the load. It will remain latched on even after the gate signal is removed until the anode current falls below its holding current (typically 5 mA for the MCR106-8G), which happens when the AC voltage crosses zero at the end of each half-cycle.
Important Note: This circuit interfaces with high-voltage AC mains. Appropriate safety precautions, including isolation and fuse protection, must be implemented to prevent electric shock or fire hazard.
Conclusion and Design Considerations
The MCR106-8G is an excellent choice for designers needing a cost-effective, sensitive, and robust SCR for medium-power AC switching. Its high sensitivity allows for easy interfacing with control logic, while its high voltage and surge ratings ensure durability in demanding environments. When designing, always consult the official onsemi datasheet for the most accurate and detailed information.
ICGOODFIND: For engineers and purchasers, the MCR106-8G represents an optimal balance of performance, sensitivity, and cost-effectiveness for AC switching and phase control applications up to 4A.
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Keywords: Silicon Controlled Rectifier (SCR), Gate Trigger Current, AC Switching, Pinout, Application Circuit
