LM219N

LM219N

The LM219N is a comparator integrated circuit manufactured by Texas Instruments (TI). It is a part of their linear series of components and falls under the family of comparators. As a comparator, it is used in circuits to compare a set voltage to another voltage and output a result based on the comparison. The LM219N has several features which give it wide applicability across many different applications.

Application Field

The LM219N can be used as a voltage switch, to turn on/off an electrical circuit depending on a given reference voltage. It can be used as an operational amplifier providing higher gain, higher response time and small footprint. It can even be used in motor control, for example to compare speed reference signal to the motor speed and therefore regulate the motor speed accordingly.

Due to its wide operating temperature range from -55 to 125 °C, and its tolerance to power-line noise, the LM219N can be used in many industrial automation and process control applications. Also, due to its low power consumption, it can be used in low-power portable applications like in medical instruments or robotics.

Other applications include signal regulation, signal conversion, signal conditioning, peak/valley detection, over voltage/under voltage protection and precision data acquisition.

Working Principle

The LM219N operates by comparing the voltages at its two input pins. Generally, one pin is supplied with a reference voltage and connected to the ground while the other is connected to the signal voltage. Depending on the values of the two voltages, the output from the LM219N will either be low or high.

The LM219N employs what is termed as open-collector voltage-comparator outputs. This is a type of output in which the output is either open (off) or connected to a common (ground) with the output device.

The key feature of such an output is the total lack of short circuit protection. If the output is connected to a switch or other current carrying device, and if that device is shorted, then there can be considerable currents on the output of the LM219N.

This is why LM219N circuits are generally put in place with protection Current limiting resistors. These resistors ensure that the maximum amount of current output by the LM219N never exceeds a given safe amount. In order to calculate the amount of current limiting resistor required relative to the desired output current, the following formula is used;

R_CL = (5V - V_OUT) / I_OUT

where R_CL, V_OUT and I_OUT are the required current limiting resistor, the desired output voltage, and the desired output current, respectively.

The LM219N can be used to provide a voltage delay through the use of its hysteresis properties. By connecting the output back to one of its input pins, the required output threshold can be adjusted with the inclusion of a resistor and capacitor. This is used in applications that require a delay in the output signal such as a switch door.

Conclusion

The LM219N is a versatile component that can be used in a variety of applications including voltage switching, motor control and signal regulation. Furthermore, its open-collector voltage-comparator output provides a design flexibility in terms of state of the output pin. It is robust and able to function in harsh environmental conditions, making it a reliable component for industrial applications.