74ls273 Dip IC

🔹 74LS273 / SN74LS273N – Octal D-Type Flip-Flop with Clear (DIP-20)

A TTL integrated circuit containing eight independent, edge-triggered D-type flip-flops with a common clock and a common asynchronous clear (reset) input. It is designed to act as an 8-bit data register or latch for temporary storage in digital systems, bus interfaces, and data pipelines.

✅ Specifications:

• Part Number: 74LS273, SN74LS273N (DIP package)

• Type: Octal D-Type Positive-Edge-Triggered Flip-Flop

• Logic Family: TTL (Low-Power Schottky)

• Supply Voltage (Vcc): 5V ±5% (4.75V to 5.25V)

• Number of Circuits: 8 independent D flip-flops

• Trigger Type: Positive-Edge Triggered (Clock Low-to-High transition)

• Inputs per Flip-Flop:

  • D0-D7: Data inputs

  • CLK: Common Clock input (active on rising edge)

  • CLR̅: Common Asynchronous Clear input (Active LOW, overrides all)

• Outputs per Flip-Flop: Q0-Q7 (Non-inverting outputs only)

• Truth Table (per flip-flop):
  CLR̅CLKDQ (next)LXXL(Asynchronous Clear)H↑HH(Store 1)H↑LL(Store 0)HL/HXQ (hold)(No Change)

• Max Clock Frequency: ~30 MHz (typical)

• Propagation Delay (CLK to Q): ~20ns (typical)

• Output Current: Can source 0.4mA, sink 8mA (standard TTL)

• Package: DIP-20 (Dual In-Line, 20-pin, through-hole)

• Operating Temperature: 0°C to +70°C (Commercial)

⚙️ Key Features:

• 8-Bit Parallel Register: Stores an entire byte of data on a single clock pulse.

• Common Control Signals: Single clock and clear line control all 8 flip-flops simultaneously, simplifying bus interfacing.

• Asynchronous Clear: Immediate reset of all outputs to LOW, independent of the clock.

• Edge-Triggered Design: Captures data only at the rising clock edge, preventing glitches from propagating.

• High Fan-Out: Can drive up to 10 standard TTL loads.

📦 Typical Applications:

• Microprocessor Data Latches: Holding data from a data bus (e.g., for display drivers, LED arrays, or output ports).

• Pipeline Registers: Storing intermediate results in digital signal processing or CPU datapaths.

• Debounced Switch Registers: Capturing the state of multiple switches or inputs simultaneously.

• Bus Interface Units: Buffering data between systems with different timing.

• Control Register: Storing configuration bits for a digital system.

• Retro Computing: Common in 8-bit computer designs (e.g., for keyboard or video buffer).

🔧 Pinout (DIP-20):

• Pin 1: CLR̅ (Common Asynchronous Clear, Active LOW)

• Pin 2: Q0 (Output 0)

• Pin 3: D0 (Data Input 0)

• Pin 4: D1 (Data Input 1)

• Pin 5: Q1 (Output 1)

• Pin 6: Q2 (Output 2)

• Pin 7: D2 (Data Input 2)

• Pin 8: D3 (Data Input 3)

• Pin 9: Q3 (Output 3)

• Pin 10: GND

• Pin 11: CLK (Common Clock, Rising Edge)

• Pin 12: Q4 (Output 4)

• Pin 13: D4 (Data Input 4)

• Pin 14: D5 (Data Input 5)

• Pin 15: Q5 (Output 5)

• Pin 16: Q6 (Output 6)

• Pin 17: D6 (Data Input 6)

• Pin 18: D7 (Data Input 7)

• Pin 19: Q7 (Output 7)

• Pin 20: VCC (+5V)

⚠️ Important Design Notes:

• Asynchronous Clear Dominates: When CLR̅ is LOW, all outputs are immediately forced to 0, overriding the clock and data inputs.

• Rising Edge Trigger: Data is captured and transferred to the output only on the rising edge (LOW-to-HIGH transition) of the clock.

• Setup and Hold Times: Data must be stable before (setup ~20ns) and after (hold ~0ns) the rising clock edge for reliable storage.

• Unused Inputs: Never leave TTL inputs floating. Tie unused D inputs to GND or Vcc via a resistor. The CLR̅ input must be tied HIGH if not used.

• Power Supply Decoupling: Always use a 0.1µF ceramic capacitor between VCC (pin 20) and GND (pin 10), placed close to the IC.

• Comparison with 74LS373: The 74LS373 is an Octal Transparent Latch with 3-state outputs, while the 74LS273 is an edge-triggered flip-flop with standard outputs.