CD4017

The CD4017 is a 16-pin CMOS integrated circuit (IC) that functions as a decade counter/divider with 10 decoded outputs.

It's widely used in electronic circuits that require sequential operation, counting, or frequency division.

Key Features and Operation

• Decade Counter: The IC counts from 0 to 9. It uses a Johnson counter structure, which has the advantage of having only one output active (HIGH) at any given time, making decoding simple.

• Decoded Outputs: It has ten outputs, labeled Q_0 through Q_9. With each clock pulse, the active output sequentially shifts from Q_0 up to Q_9, and then cycles back to Q_0. Only the current count's output pin is HIGH; all others are LOW.

• Clock Input (Pin 14 - CLK): The counter advances by one step on the rising edge (low-to-high transition) of the clock pulse applied to this pin.

• Clock Inhibit (Pin 13 - CI/CLK EN):

  • When this pin is LOW (grounded for normal operation), the counter is enabled and responds to the clock pulses.

  • When this pin is HIGH, the counter is disabled, and the count will hold at its current state regardless of clock pulses.

• Reset (Pin 15 - MR):

  • When this pin is momentarily pulled HIGH, the counter immediately resets, and the output Q_0 becomes HIGH (count = 0).

  • For normal counting operation, this pin must be held LOW (grounded). This pin can also be connected to any of the outputs (Q_1 to Q_9) to create a counter that counts up to a specific number (a "divide-by-N" counter). For example, connecting Q_6 to the Reset pin makes it count from 0 to 5, and then reset.

• Carry Out (Pin 12 - CO): This pin goes HIGH after the counter completes a full cycle of 10 clock pulses (specifically, it is LOW for Q_0 through Q_4 and HIGH for Q_5 through Q_9). It is typically used to cascade multiple CD4017 ICs to count higher than 10.

• Supply Voltage: It supports a wide supply voltage range, typically from 3V to 15V (or up to 18V for some variants).

Common Applications

Due to its sequential output nature, the CD4017 is often used in:

• Sequential LED Light Circuits: Also known as LED Chasers or "Knight Rider" lights.

• Frequency Division: It can divide an input frequency by a factor of 10, or less if the reset pin is used.

• Timing Circuits and Control Circuits.

Pin Configuration (Summary)

Learn more about building a simple circuit with this IC by watching this CD4017 Decade Counter YouTube tutorial.