7447 BCD to 7-Segment Decoder/Driver IC (DIP)

Overview: 7447 BCD to 7-Segment Decoder/Driver IC (DIP)

The 7447 BCD to 7-Segment Decoder/Driver converts a 4-bit binary coded decimal input into the seven-segment signals needed to display digits 0 to 9 on common-anode LED displays. With open-collector, active-LOW outputs and TTL-compatible inputs, the 7447 simplifies numeric display designs in counters, clocks, meters, microcontroller projects, and educational kits.

Key Features

• BCD (A, B, C, D) to seven-segment decode for digits 0 to 9
• Common-anode display driver with open-collector, active-LOW outputs (a–g)
• Control pins: LT (Lamp Test), BI̅ (Blanking Input), RBI and RBO for cascading and blanking
• TTL-compatible inputs; nominal 5 V supply for rapid switching
• Standard DIP-16 package, compatible with breadboards and through-hole PCBs

Technical Specifications

• Supply voltage: 4.75 to 5.25 V (TTL)
• Inputs: A, B, C, D (BCD), LT, BI̅, RBI
• Outputs: a, b, c, d, e, f, g (active-LOW), plus RBO
• Display type: Common-anode 7-segment
• Package: DIP-16

Control Pins and Functions

• LT (Lamp Test): Forces all segment outputs LOW to illuminate every segment for testing.
• BI̅ (Blanking Input): When asserted, blanks the display by turning off all segments.
• RBI (Ripple Blanking In) and RBO (Ripple Blanking Out): Support leading-zero suppression when cascading multiple digits. Use RBI from the next digit to propagate blanking signals.

Wiring and Usage Tips

• Connect the display common anode to +5 V.
• Place a current-limiting resistor in series with each segment between the segment pin and the 7447 output to limit LED current.
• Inputs A, B, C, D receive the BCD code. Drive them with TTL outputs or a microcontroller interface at 5 V logic levels.
• Use LT for quick lamp tests during manufacturing or debugging. Use BI̅ to blank the display for power saving or visual effects.
• For multi-digit displays, cascade RBO of the less significant digit to RBI of the next digit to implement ripple blanking and leading-zero suppression.

Typical Applications

• Up/down counters and frequency displays
• Digital clocks, timers, and stopwatches
• Microcontroller numeric readouts and training labs
• Educational kits, prototyping boards, and hobby electronics

Package and Prototyping

The DIP-16 package makes the 7447 ideal for breadboard prototyping and through-hole PCB designs. Its TTL-level inputs allow direct interfacing with legacy logic families and many microcontrollers when run at standard 5 V.

Usage tip: When wiring, remember the 7447 outputs are active-LOW open-collector. The common anode goes to +5 V and each segment line should include a resistor to limit LED current.

Note: Images are for illustration purposes only.