74ls48 dip IC

🔹 74LS48 / SN74LS48N – BCD-to-7-Segment Decoder/Driver IC (DIP-16)

A classic TTL integrated circuit designed to decode a 4-bit Binary Coded Decimal (BCD) input and drive a common-cathode 7-segment LED display directly. It includes internal pull-up resistors and features for blanking and lamp test, simplifying display interfacing in digital clocks, counters, and instrument panels.

✅ Specifications:

• Part Number: 74LS48, SN74LS48N (DIP package)

• Type: BCD-to-7-Segment Decoder/Driver

• Logic Family: TTL (Low-Power Schottky)

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

• Input Type: BCD (4-bit: A, B, C, D, where A is LSB or MSB – check datasheet)

• Output Type: Active-High, for Common-Cathode 7-segment displays

• Output Current: Can sink up to 24mA per segment (typical)

• Maximum Clock Frequency: ~25 MHz (for dynamic control)

• Package: DIP-16 (Dual In-Line, 16-pin, through-hole)

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

• Key Control Pins:

  • LT (Lamp Test, Pin 3): Active LOW. When LOW, all segments turn ON.

  • BI/RBO (Blanking Input/Ripple Blanking Output, Pin 4): Dual-purpose. As input (BI), active LOW to force blank display. As output (RBO), goes LOW when display is zero and RBI is LOW (for leading-zero blanking).

  • RBI (Ripple Blanking Input, Pin 5): Active LOW. When LOW and input is 0, forces display blank and RBO goes LOW.

• Quantity: 1 piece (implied by part number listing)

⚙️ Features:

• Integrated Driver: Has built-in output transistors to directly drive common-cathode LED displays without external buffers (for typical displays).

• Ripple Blanking: Allows easy suppression of leading or trailing zeros in multi-digit displays.

• Lamp Test Function: Allows testing all display segments simultaneously.

• Standard TTL Compatibility: Directly interfaces with other TTL logic (74LS series counters, latches) and 5V microcontrollers.

• Widely Available & Understood: A staple in digital electronics education and legacy designs.

📦 Typical Applications:

• Digital Counters & Timers: Driving displays for frequency counters, stopwatches, or event counters.

• Instrumentation Panels: Numeric readouts for voltmeters, multimeters, or control systems.

• Educational Kits & Prototyping: Learning about BCD, decoders, and display interfacing.

• Retro & DIY Clocks: Building classic digital clocks with discrete logic.

• Scoreboards & Simple Numeric Displays.

🔧 Basic Connection (Single Digit):

1. Power: Connect VCC (Pin 16) to +5V and GND (Pin 8) to ground.

2. BCD Input: Connect 4-bit BCD data (e.g., from a counter like 74LS90) to inputs A (LSB), B, C, D (MSB) (Pins 7,1,2,6 – verify order in datasheet).

3. Display: Connect outputs a-g (Pins 13,12,11,10,9,15,14) to the corresponding segment pins of a common-cathode 7-segment display.

4. Current Limiting: Place a current-limiting resistor (180Ω to 330Ω typical) between each segment output and the display OR a single resistor on the common cathode (if multiplexing).

5. Control Pins: For normal operation, tie LT (Pin 3) and BI/RBO (Pin 4) HIGH (to Vcc via a resistor or directly). Tie RBI (Pin 5) HIGH if ripple blanking is not needed.

⚠️ Critical Design Notes & Limitations:

• Common-Cathode Only: Only drives common-cathode displays. For common-anode displays, use the 74LS47.

• 5V Only: Requires a stable 5V power supply. Do not exceed 5.25V.

• Current Limits: While it can sink up to 24mA per segment, check total package power dissipation. For very bright displays or high multiplex rates, consider using external transistor drivers.

• Unused Inputs: For TTL logic, unused inputs should be tied HIGH (to Vcc through a 1kΩ resistor or directly) to ensure proper operation and avoid noise.

• Not for Direct High-Voltage/High-Current: Cannot drive incandescent, VFD, or large displays directly. Requires drivers.