CD4017 Pinout
CD4017 Decade Counter · Decade Johnson counter; 10 outputs that go high in sequence; common for LED chasers / frequency division.
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | Q5 | Output | Decoded output 5 |
| 2 | Q1 | Output | Decoded output 1 |
| 3 | Q0 | Output | Decoded output 0 (high after reset) |
| 4 | Q2 | Output | Decoded output 2 |
| 5 | Q6 | Output | Decoded output 6 |
| 6 | Q7 | Output | Decoded output 7 |
| 7 | Q3 | Output | Decoded output 3 |
| 8 | VSS · GND | GND | Ground |
| 9 | Q8 | Output | Decoded output 8 |
| 10 | Q4 | Output | Decoded output 4 |
| 11 | Q9 | Output | Decoded output 9 |
| 12 | CO · CARRY | Output | Carry output (one pulse every 10 counts; can be cascaded) |
| 13 | CE · /INH | Control | Clock enable (active-low; high pauses counting) |
| 14 | CLK | Control | Clock input (counts on rising edge) |
| 15 | MR · RESET | Control | Reset (active-high, returns to Q0) |
| 16 | VDD | Power | Supply + (3–15V) |
How to read the CD4017 pinout
- 01
Find pin 1
One end of the chip has a half-circle notch or a dot; with the notch facing up, the top-left pin is pin 1.
- 02
Count counter-clockwise
Count counter-clockwise from pin 1: go down the left side first, then up the right side from the bottom.
- 03
Check the table below
Look up each pin's function by number in the table below; power/ground are color-coded, and alternate-function signals are in parentheses.
Frequently asked questions
Why are the output pins in a scrambled order?
This is the CD4017's famous "scrambled" pinout: Q0–Q9 are not physically contiguous (e.g. 3=Q0, 2=Q1, 4=Q2…). Wire it per the table; don't guess from the pin numbers.
How do I make an N-output LED chaser?
Connect the (N+1)th output to MR (pin 15) to reset when it reaches N, giving a 1…N loop; CO (pin 12) can cascade the next chip for more outputs.
How do I connect CE (pin 13) if unused?
Tie it to ground (enabled). Pull it high to pause counting.
Pinout data comes from TI CD4017B datasheet (standard DIP-16 numbering). Refer to the actual device datasheet as authoritative for the pinout.