74LS175 Quad D-type flip-flop with clear
The 74LS175 holds four D flip-flops that share one clock and one active-low clear. On each rising clock edge all four copy their D inputs at once, which makes it a 4-bit register with both true and complemented outputs.
74LS175 pinout
Top view of the 16-pin DIP package. Pin 1 is at the bottom left, beside the notch, and the numbers run anticlockwise. Power is on pin 16 (VCC, +5 V) and pin 8 (GND).
| Pin | Name | Type | What it is |
|---|---|---|---|
| 1 | CLR′ | Input | Input, active-low |
| 2 | 1Q | Output | Totem-pole output |
| 3 | 1Q′ | Output | Totem-pole output, active-low |
| 4 | 1D | Input | Input |
| 5 | 2D | Input | Input |
| 6 | 2Q′ | Output | Totem-pole output, active-low |
| 7 | 2Q | Output | Totem-pole output |
| 8 | GND | Ground | 0 V |
| 9 | CLK | Input | Input |
| 10 | 3Q | Output | Totem-pole output |
| 11 | 3Q′ | Output | Totem-pole output, active-low |
| 12 | 3D | Input | Input |
| 13 | 4D | Input | Input |
| 14 | 4Q′ | Output | Totem-pole output, active-low |
| 15 | 4Q | Output | Totem-pole output |
| 16 | VCC | Power | +5 V supply |
74LS175 function table
| CLR′ | CLK | D | Q | Q′ |
|---|---|---|---|---|
| 0 | X | X | 0 | 1 |
| 1 | ↑ | 1 | 1 | 0 |
| 1 | ↑ | 0 | 0 | 1 |
| 1 | 0 | X | Q0 | Q0′ |
↑ is the clock's rising edge. The clock and the clear are shared by all four.
What the 74LS175 is used for
- A 4-bit register that holds a value between clock edges
- The state register of a small state machine
- Latching a BCD digit for a display
Electrical summary
| Package | 16-pin DIP |
| Supply voltage | 5 V (4.75 V to 5.25 V) |
| Output type | Totem-pole — drives both high and low |
| Output current, low | sinks up to 8 mA |
| Output current, high | sources up to 0.4 mA |
| Input current, low | 0.4 mA out of each input held low |
| Fan-out | one output can drive about 20 LS inputs |
Typical figures for quick reference when planning a board. Check the manufacturer's datasheet for limits and timing before committing a design. The 74HC175 and 74HCT175 use the same pin numbers, with different electrical values.
The 74LS175 and the Breadboard Simulator
The 74LS175 is not in the Breadboard Simulator's parts library yet — this page is a reference. The simulator seats the gates, decoders, multiplexers, adders and buffers marked on the chips page, so the logic around a 74LS175 can be planned and wired there.