7447 BCD to 7-Segment Decoder Driver IC | Pro Tronix

Product Description

The 7447 BCD to 7-Segment Decoder Driver IC is an essential high-speed TTL digital logic integrated circuit designed to translate 4-bit Binary Coded Decimal (BCD) inputs directly into signal outputs for driving Common Anode 7-segment LED displays. The chip accepts standard binary logic values from 0 to 9 (0000 to 1001) and decodes them into the active-LOW output signals needed to display clear, recognizable decimal digits on a display readout.

Equipped with high-voltage, open-collector outputs that can sink up to 24 mA per segment, the 7447 can directly drive 7-segment display segments through current-limiting resistors without requiring extra driver transistors. It includes advanced display management features such as Lamp Test (LT) for testing segment functionality, Ripple Blanking Input (RBI) and Ripple Blanking Output (RBO) for leading and trailing zero suppression in multi-digit displays, and a Blanking Input (BI) line for intensity modulation. Housed in a standard 16-pin DIP package operating on a 5V DC supply, it interfaces seamlessly with microcontrollers, discrete counters (like the 7490), and digital logic training kits.

⚠️ Display Compatibility Tip: The 7447 features active-LOW open-collector outputs designed specifically for Common Anode 7-segment displays. Connect the common pin of your display to VCC (+5V) and connect each segment pin (a through g) to the corresponding 7447 output pin through an appropriate current-limiting resistor (typically 220 Ohm to 330 Ohm). Floating or un-terminated test inputs (Pin 3 LT and Pin 5 RBI) should be tied HIGH (+5V) during normal operation to prevent unwanted blanking.

Technical & Logic Architecture

This BCD-to-7-segment driver delivers precise display control and system functionality:

• Common Anode Direct Drive: Active-LOW open-collector outputs designed to sink segment current directly from common anode displays.

• Automatic Zero Blanking: Built-in Ripple Blanking Input (RBI) and Ripple Blanking Output (RBO) enable automatic leading zero suppression across multi-digit displays.

• Display Testing & Blanking Control: Dedicated Lamp Test (LT) pin overrides inputs to light up all segments for display diagnostics; Blanking Input (BI) allows PWM intensity control or full display shutdown.

• Breadboard-Friendly Package: Standard 16-pin Dual In-Line Package (DIP-16) for fast prototyping on breadboards and IC sockets.

7447 Truth Table (Function Table)

Key Terms for Truth Table:

• H: High Voltage Level (Logic 1 / VCC)

• L: Low Voltage Level (Logic 0 / GND)

• X: Don’t Care (High or Low)

• BCD Inputs: A is Least Significant Bit (LSB / Bit 0), D is Most Significant Bit (MSB / Bit 3).

• Note: Table assumes LT (Pin 3) and BI/RBO (Pin 4) are held HIGH during standard numeric operation.

7447 Pinout Description & Logic Functions

• Pin 1 – Input C: Binary bit 2 input line.

• Pin 2 – Input B: Binary bit 1 input line.

• Pin 3 – LT (Lamp Test): Active-LOW input. When pulled LOW, turns ON all segments to test the display.

• Pin 4 – BI / RBO (Blanking Input / Ripple Blanking Output): Dual-function pin. Input LOW turns OFF all segments; acts as output for zero-suppression cascades.

• Pin 5 – RBI (Ripple Blanking Input): Active-LOW input used for leading zero suppression in multi-digit displays.

• Pin 6 – Input A (LSB): Binary bit 0 input line.

• Pin 7 – Input D (MSB): Binary bit 3 input line.

• Pin 8 – GND: Ground reference pin (0V).

• Pin 9 – Output e: Active-LOW segment drive output for display segment e.

• Pin 10 – Output d: Active-LOW segment drive output for display segment d.

• Pin 11 – Output c: Active-LOW segment drive output for display segment c.

• Pin 12 – Output b: Active-LOW segment drive output for display segment b.

• Pin 13 – Output a: Active-LOW segment drive output for display segment a.

• Pin 14 – Output g: Active-LOW segment drive output for display segment g.

• Pin 15 – Output f: Active-LOW segment drive output for display segment f.

• Pin 16 – VCC: Positive power supply input pin (+5V DC nominal).

Operating Modes Summary

1. Standard BCD Decoding: Converts 4-bit binary counter values into numeric 7-segment glyphs (0–9).

2. Display Diagnostic Mode: Pull Pin 3 (LT) LOW to check if any segments on the connected display are burnt out.

3. Leading Zero Suppression: Chain Pin 4 (RBO) of one IC to Pin 5 (RBI) of the next to turn off unneeded zeros (e.g., displaying “5” instead of “005”).

Applications

• Digital Counter Displays: Driving common anode numeric readouts for frequency counters, digital clocks, and event meters.

• Instrumentation Readouts: Converting binary data from sensors or microcontrollers to visible decimal numbers.

• Educational Logic Labs: Teaching digital logic decoding, display multiplexing, and binary representation.

Technical Specifications

What’s in the Box

• 1 x 7447 BCD to 7-Segment Decoder Driver IC (DIP-16).

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🛠️ Complete Your Breadboard Setup

To quickly wire and test the 7447 BCD to 7-Segment Decoder Driver IC without soldering, make sure to check out our collection of breadboards, prototype boards, and jumper wires:

• Breadboards & Prototype PCBs: Explore our full range of solderless breadboards and prototyping boards for easy circuit assembly: Pro Tronix Breadboards & PCBs

• Jumper Wires & Connecting Cables: Grab high-quality male-to-male and male-to-female jumper wires to connect your IC pins to power and signal lines: Pro Tronix Wires & Cables Collection