How to Use LM393: Examples, Pinouts, and Specs

The LM393 is a widely used dual differential comparator integrated circuit, capable of comparing two input voltages and providing a digital output to indicate which input is higher. It is designed for use in level detection, battery monitoring, and other applications where a simple voltage comparison is required.

• Voltage level detection
• Battery chargers
• Window comparators
• Relay drivers
• Simple analog to digital converters
• Motor control circuits

• Supply Voltage Range: 2.0V to 36V, or ±1.0V to ±18V
• Input Bias Current: 25 nA (typical)
• Input Offset Current: ±5 nA (typical)
• Offset Voltage: ±1 mV (typical)
• Supply Current: 0.8 mA (typical)
• Response Time: 1.3 µs (typical)
• Operating Temperature Range: 0°C to +70°C

1. Connect the VCC pin to a positive supply voltage within the specified range.
2. Connect the GND pin to the ground of the power supply.
3. Apply the reference voltage to the non-inverting input (IN1+ or IN2+).
4. Apply the variable voltage to be compared to the inverting input (IN1- or IN2-).
5. Connect the output (OUT1 or OUT2) to the digital input of a microcontroller or use it to drive a relay or an LED with appropriate current limiting.

• Always ensure that the supply voltage does not exceed the maximum rating.
• Use bypass capacitors near the power supply pins to filter out noise and provide a stable operation.
• Avoid applying voltages to the input pins that are outside the range of the power supply rails.
• The outputs are open-collector, which means they require a pull-up resistor to the supply voltage to function correctly.

// Example code for using LM393 with Arduino UNO

const int comparatorOutputPin = 2; // Connect to OUT1 or OUT2 of LM393
const int ledPin = 13; // Onboard LED

void setup() {
  pinMode(comparatorOutputPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int comparatorState = digitalRead(comparatorOutputPin);
  if (comparatorState == HIGH) {
    // Voltage at IN1- or IN2- is higher than IN1+ or IN2+
    digitalWrite(ledPin, HIGH);
  } else {
    // Voltage at IN1+ or IN2+ is higher than IN1- or IN2-
    digitalWrite(ledPin, LOW);
  }
}

• No Output Signal: Ensure that the power supply is connected correctly and the input voltages are within the specified range.
• Output Always High or Low: Check the input voltages and the connection of the pull-up resistor on the output pin.
• Erratic Behavior: Place a bypass capacitor near the power supply pins to filter out noise.

• Verify the orientation of the LM393 in the circuit.
• Use a multimeter to check the voltages at the input pins.
• Ensure that the pull-up resistor value is appropriate for the supply voltage and the load connected to the output.

Q: Can the LM393 be used with a single supply voltage? A: Yes, the LM393 can operate with a single supply voltage ranging from 2.0V to 36V.

Q: What is the purpose of the pull-up resistor on the output? A: The LM393 has an open-collector output, which requires an external pull-up resistor to provide a high level when the output transistor is off.

Q: Can the LM393 outputs sink current? A: Yes, the outputs can sink current, but the maximum current should not exceed the specified limit in the datasheet.

Q: Is the LM393 suitable for high-speed applications? A: The LM393 has a typical response time of 1.3 µs, which may be suitable for some high-speed applications, but there are faster comparators available for very high-speed needs.

Note: The manufacturer part ID "WPSE347" and the claim that Arduino is the manufacturer of the LM393 are incorrect. The LM393 is a generic part manufactured by various companies, and Arduino does not manufacture this component. The part ID provided does not correspond to a known manufacturer's part number for the LM393. Always refer to the datasheet from the specific manufacturer of your component for the most accurate information.