LM393: Pinout, Features, Applications, and Working Principle

LM393 Pinout

The LM393 comes in an 8-pin dual inline package (DIP-8) or an 8-pin small outline package (SOP-8). The pinout for both packages is identical, as shown in the table below:

Features of LM393

The LM393 offers several key features that make it an attractive choice for various applications:

1. Dual Comparators: The LM393 contains two independent Voltage Comparators in a single package, saving space and reducing component count.

2. Wide Supply Voltage Range: It can operate with a supply voltage ranging from 2V to 36V, allowing for flexibility in design.

3. Low Input Bias Current: The LM393 has a low input bias current of 25nA (typical), which minimizes the loading effect on the input signal sources.

4. Low Input Offset Voltage: With a typical input offset voltage of 2mV, the LM393 provides accurate comparisons even with small input voltage differences.

5. Open-Collector Outputs: The comparator outputs are open-collector, allowing for easy interfacing with various logic families and the ability to perform wired-AND logic.

6. Wide Operating Temperature Range: The LM393 can operate in a temperature range of -25°C to +85°C (for the commercial grade) or -55°C to +125°C (for the industrial grade), making it suitable for a variety of environments.

Applications of LM393

The LM393 finds use in a wide range of electronic applications, including:

1. Voltage Level Detection: The LM393 can be used to detect when a voltage level crosses a certain threshold, making it useful in battery monitoring, undervoltage protection, and overvoltage detection circuits.

2. Zero-Crossing Detection: By comparing a signal with a reference voltage (usually ground), the LM393 can detect the zero-crossing points of AC signals, which is essential in phase control and synchronization applications.

3. Window Comparator: Two LM393 comparators can be combined to create a window comparator circuit that detects when a signal falls within a specific voltage range.

4. Pulse Width Modulation (PWM) Generation: The LM393 can be used in conjunction with an RC network to generate PWM signals for controlling motors, LEDs, or other devices.

5. Analog-to-Digital Conversion: In simple ADC circuits, such as the flash ADC, the LM393 can be used as a comparator to compare the input analog signal with reference voltages and generate digital outputs.

6. Schmitt Trigger: By adding positive feedback to the comparator circuit, the LM393 can be configured as a Schmitt trigger, providing hysteresis and noise immunity to the input signal.

Working Principle of LM393

The LM393 is a voltage comparator that compares two analog input voltages and outputs a digital signal indicating which input is greater. Each comparator in the LM393 has two inputs: a non-inverting input (IN+) and an inverting input (IN-).

When the voltage at the non-inverting input (IN+) is higher than the voltage at the inverting input (IN-), the output of the comparator goes high, typically close to the supply voltage (VCC). Conversely, when the voltage at the inverting input (IN-) is higher than the voltage at the non-inverting input (IN+), the output of the comparator goes low, typically close to the ground potential (GND).

The output of the LM393 is an open-collector, meaning that it requires an external pull-up resistor to provide a high output state. The value of the pull-up resistor depends on the desired output voltage level and the load current.

The comparator’s output can be used to drive other circuits, such as logic gates, LEDs, or transistors, depending on the application requirements.

Frequently Asked Questions (FAQ)

1. What is the difference between the LM393 and the LM339?
   The LM393 contains two comparators, while the LM339 contains four comparators in a single package. Both ICs share similar electrical characteristics and pinouts, but the LM339 offers more comparators for applications that require them.

2. Can the LM393 be used with a single power supply?
   Yes, the LM393 can operate with a single power supply. The input and output voltages are referenced to the ground (GND) pin, and the comparator can handle input voltages ranging from ground to the positive supply voltage (VCC).

3. What is the purpose of the open-collector output in the LM393?
   The open-collector output allows the LM393 to interface with various logic families and perform wired-AND logic. It also enables the comparator to drive loads that require more current than the IC can provide directly, by using an external pull-up resistor.

4. How do I set the threshold voltage for the LM393 comparator?
   The threshold voltage is set by applying a reference voltage to one of the comparator’s inputs (usually the inverting input) while the other input receives the signal to be compared. The reference voltage can be generated using a voltage divider, a potentiometer, or a fixed voltage source, depending on the application requirements.

5. What is the input offset voltage, and how does it affect the LM393’s performance?
   The input offset voltage is the voltage difference required between the inputs to make the comparator output change states when both inputs are equal. A lower input offset voltage means the comparator can detect smaller voltage differences accurately. The LM393 has a typical input offset voltage of 2mV, which is suitable for most general-purpose applications.

The LM393 is a versatile and widely used dual differential comparator IC that offers reliable performance, low power consumption, and a wide operating voltage range. Its pinout, features, and working principle make it an excellent choice for various electronic applications, such as voltage level detection, zero-crossing detection, and PWM generation. By understanding the LM393’s characteristics and its application in different circuits, designers can effectively incorporate this comparator into their projects.