Texas Instruments SN74LS47DG4

Overview

SN74LS47DG4 from Texas Instruments is a BCD-to-seven-segment decoder/driver IC designed for direct interface with common-anode LED displays. It features active-low outputs, built-in lamp test and blanking inputs, TTL-compatible BCD inputs (A–D), and operates over 0°C to 70°C. Used in digital panel meters, calculators, and industrial status indicators requiring discrete numeric display drive.

For engineers reviewing the SN74LS47DG4 datasheet, SN74LS47DG4 pinout, SN74LS47DG4 application, or SN74LS47DG4 equivalent, key selection factors include its active-low open-collector outputs, integrated ripple-blanking input for cascaded displays, latch-free combinational logic, and compatibility with legacy TTL logic families in industrial control panels and test equipment.

Technical Context

The SN74LS47DG4 implements fully decoded BCD-to-seven-segment logic with internal NAND-OR-INVERT gates driving seven open-collector outputs (a–g). Its functional architecture includes a ripple-blank input (RBI) and output (RBO) for multi-digit blanking control, a lamp test input (LT̅) that forces all segments ON, and a blanking input (BI̅) that overrides decoding to force all outputs OFF.

All inputs are TTL-compatible with V_IH = 2.0 V min and V_IL = 0.8 V max; outputs sink up to 40 mA per segment at V_OL ≤ 0.5 V. The device contains no latches or memory-output states change synchronously with input BCD transitions.

Key Specifications

Pinout & Package

SN74LS47DG4 is supplied in a 16-pin SOIC (D) package, 7.5 mm wide, with 1.27 mm pitch and 2.00 mm maximum height. Pin 1 is marked by a beveled corner or notch on the package top surface.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-seven-segment decoder/driver applications.

Compared with SN74LS47N and SN74LS47DR, the SN74LS47DG4 offers identical core functionality in a SOIC-16 tube-packaged variant - providing mid-volume procurement flexibility, manual rework accessibility, and compatibility with both automated and semi-automated assembly lines without performance trade-offs.

Availability

SN74LS47DG4 is available at Aetrix Electronics and suitable for digital instrumentation, industrial HMIs, and educational lab kits requiring stable component supply and long-term obsolescence management.

Supply support for SN74LS47DG4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and consumer reach.

The SN74LS47DG4 belongs to TI's legacy 74LS logic family, engineered for reliable BCD-driven LED display interfaces in cost-sensitive, non-microcontroller-based systems where simplicity and deterministic behavior are critical.

FAQ

What is the primary function of the SN74LS47DG4?

The SN74LS47DG4 is a BCD-to-seven-segment decoder/driver IC that converts a 4-bit binary-coded decimal input into active-low signals for driving common-anode LED displays. It provides seven open-collector outputs (a–g), plus lamp test (LT̅), blanking (BI̅), and ripple-blanking (RBI/RBO) control functions - all implemented in standard 74LS TTL logic with no internal latching or clocking.

Can the SN74LS47DG4 drive common-cathode LED displays?

No, the SN74LS47DG4 cannot directly drive common-cathode LED displays. Its outputs are active-low open-collector, designed specifically for common-anode configurations where the LED anodes connect to V_CC and cathodes connect to the SN74LS47DG4 outputs. To use with common-cathode displays, an external inverter stage or alternative driver such as the SN7447 (which is functionally identical but historically marked for common-anode use) would be required - though SN7447 and SN74LS47 share identical pinout and logic.

What is the purpose of the RBI and RBO pins on the SN74LS47DG4?

The RBI (Ripple Blanking Input) and RBO (Ripple Blanking Output) pins enable zero-suppression across multiple SN74LS47DG4 devices in a multi-digit display. When RBI is pulled LOW and the decoded digit is zero, RBO goes LOW to signal adjacent (less-significant) digits to blank - eliminating leading zeros in numbers like "0042". This function operates entirely in hardware with no software or timing dependencies, making it ideal for real-time instrumentation displays.

Does the SN74LS47DG4 require external pull-up resistors on its segment outputs?

Yes, the SN74LS47DG4 requires external pull-up resistors on all seven segment outputs (a–g) when driving common-anode LEDs. Because its outputs are active-low open-collector, each output must be pulled to V_CC (typically +5 V) through a current-limiting resistor - typically 330 Ω to 1 kΩ depending on LED forward voltage and desired brightness. Omitting pull-ups results in floating outputs and unpredictable display behavior.

Is the SN74LS47DG4 compatible with modern microcontrollers such as those using 3.3 V logic?

The SN74LS47DG4 accepts TTL-level inputs (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), making it compatible with 3.3 V microcontrollers only if their GPIO outputs meet these thresholds - many 3.3 V CMOS outputs do not guarantee V_IH ≥ 2.0 V under load. For reliable interfacing, use a level-shifting buffer or select a 74HCT-series equivalent (e.g., 74HCT4511) which guarantees 3.3 V–5 V bidirectional compatibility while retaining similar decode functionality.