How to Use CD4093: Examples, Pinouts, and Specs

The CD4093 is a quad 2-input NAND Schmitt trigger IC manufactured by Texas Instruments. It is designed to provide a high degree of noise immunity and is widely used in digital circuits for signal conditioning, waveform shaping, and logic-level conversion. The Schmitt trigger functionality ensures that the output switches cleanly between logic states, even when the input signal is noisy or has slow transitions.

• Signal conditioning in noisy environments
• Waveform generation and shaping
• Pulse-width modulation (PWM) circuits
• Oscillators and timers
• Logic-level conversion
• Debouncing mechanical switches

The following table outlines the key technical specifications of the CD4093:

The CD4093 has a total of 14 pins. The pinout and their descriptions are as follows:

1. Power Supply: Connect the VDD pin (Pin 14) to the positive supply voltage (3V to 15V) and the VSS pin (Pin 7) to ground.
2. Inputs: Apply the input signals to the respective A and B pins of the NAND gates. Ensure the input voltage levels are within the specified range (0V to VDD).
3. Outputs: The output of each NAND gate is available on the corresponding Q pin. The output will switch between 0V and VDD based on the logic levels of the inputs.
4. Schmitt Trigger Behavior: The Schmitt trigger inputs provide hysteresis, which ensures clean transitions at the output even with noisy or slow-changing input signals.

• Decoupling Capacitor: Place a 0.1 µF ceramic capacitor close to the VDD and VSS pins to filter out power supply noise.
• Unused Inputs: Tie unused inputs to VDD or VSS to prevent floating inputs, which can cause erratic behavior.
• Input Voltage: Do not exceed the supply voltage (VDD) on any input pin to avoid damaging the IC.
• Load Current: Ensure the output current does not exceed the maximum rating of ±10 mA to prevent overheating or damage.

The CD4093 can be used to debounce a mechanical switch and provide a clean digital signal to an Arduino UNO. Below is an example circuit and code:

• Connect the switch to one input of a NAND gate (e.g., A1) and tie the other input (B1) to VDD.
• The output (Q1) of the NAND gate is connected to an Arduino digital input pin.
• Use a pull-down resistor (e.g., 10 kΩ) on the switch input to ensure a defined logic level when the switch is open.

// Define the digital input pin connected to the CD4093 output
const int inputPin = 2;

void setup() {
  pinMode(inputPin, INPUT); // Set the pin as an input
  Serial.begin(9600);       // Initialize serial communication
}

void loop() {
  int state = digitalRead(inputPin); // Read the state of the input pin
  if (state == HIGH) {
    Serial.println("Switch is ON"); // Print message if switch is pressed
  } else {
    Serial.println("Switch is OFF"); // Print message if switch is not pressed
  }
  delay(100); // Add a small delay to avoid spamming the serial monitor
}

1. No Output Signal

   • Cause: Power supply not connected or incorrect voltage.
   • Solution: Verify that VDD and VSS are properly connected and the supply voltage is within the specified range.

2. Erratic Output Behavior

   • Cause: Floating inputs or noisy power supply.
   • Solution: Tie unused inputs to VDD or VSS and add a decoupling capacitor near the IC.

3. Output Voltage Too Low

   • Cause: Excessive load current or damaged IC.
   • Solution: Ensure the load current does not exceed ±10 mA. Replace the IC if damaged.

4. Slow Response Time

   • Cause: Low supply voltage or high input capacitance.
   • Solution: Increase the supply voltage (within the specified range) or reduce input capacitance.

Q1: Can the CD4093 operate at 3.3V?
A1: Yes, the CD4093 can operate at a supply voltage as low as 3V, making it compatible with 3.3V systems.

Q2: What is the purpose of the Schmitt trigger in the CD4093?
A2: The Schmitt trigger provides hysteresis, which ensures clean output transitions even with noisy or slow-changing input signals.

Q3: Can the CD4093 be used to create an oscillator?
A3: Yes, the CD4093 can be configured as an oscillator by connecting external resistors and capacitors to its inputs and outputs.

Q4: Is the CD4093 compatible with TTL logic levels?
A4: The CD4093 is a CMOS device and may not directly interface with TTL logic levels. Use a level shifter if necessary.