Texas Instruments SN7447AN

Overview

SN7447AN from Texas Instruments is a BCD-to-seven-segment decoder/driver IC designed for direct interface with common-anode LED displays. It accepts 4-bit binary-coded decimal (BCD) input, provides active-low segment outputs (a–g), includes lamp test (LT̅), ripple blanking input (RBI̅), and blanking input (BI̅/RBO̅), and operates over 0°C to 70°C in a 16-pin PDIP package.

For engineers reviewing the SN7447AN datasheet, SN7447AN pinout, SN7447AN application, or SN7447AN equivalent, this device is selected for discrete LED display control in legacy instrumentation, digital panel meters, and industrial status indicators where TTL-compatible logic levels and direct anode-driving capability are required.

Technical Context

The SN7447AN implements combinational logic decoding of BCD inputs (A0–A3) into seven active-low segment drive signals (a–g) with built-in NAND-based output drivers capable of sinking ≥40 mA per segment. Its internal logic supports dynamic blanking via BI̅/RBO̅ (active-low blanking input / ripple blanking output) and LT̅ (lamp test), enabling cascaded multi-digit display systems without external gating.

It belongs to the TTL family with standard Schottky-clamped transistor-transistor logic (TTL) input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output voltage specifications (VOH = 2.4 V min at IOL = 16 mA, VOL = 0.5 V max at IOL = 16 mA). The device does not include latching or clocked functionality - operation is purely combinational and asynchronous.

Key Specifications

Pinout & Package

SN7447AN uses a 16-pin PDIP (plastic dual in-line package) with 0.3" body width and 0.1" lead pitch. Pin 1 is located at the left end of the top row, identified by a notch or dot marking on the package.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN7447AN, SN74LS47N offers faster propagation and lower quiescent current while maintaining full pin and functional compatibility; 74HC4511 provides broader supply flexibility but requires hardware changes due to output polarity and voltage domain mismatch.

Availability

SN7447AN is available at Aetrix Electronics and suitable for digital panel meters, industrial status displays, and legacy equipment repair requiring stable component supply and long-term obsolescence management.

Supply support for SN7447AN 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 and automotive qualification.

The SN74xx series was developed in the 1970s as foundational TTL logic for digital system design, with the SN7447A variant optimized for LED display interfacing in instrumentation and control panels.

FAQ

What is the maximum output current per segment on the SN7447AN?

The SN7447AN can sink up to 40 mA per segment output (pins a–g) under specified conditions (VCC = 5 V, TA = 25°C). This allows direct driving of standard common-anode LED segments without external transistors, though continuous operation near this limit requires thermal consideration and appropriate current-limiting resistors.

Can SN7447AN drive common-cathode LED displays?

No, SN7447AN cannot directly drive common-cathode LED displays. Its outputs are active-low and designed to sink current into common-anode configurations. Driving common-cathode displays would require external inverters or level-shifting circuitry, making SN7447AN unsuitable for that topology without redesign.

What happens when invalid BCD codes (1010–1111) are applied to SN7447AN inputs?

When inputs A3–A0 represent values 10 (1010) through 15 (1111), SN7447AN produces no valid segment outputs - all a–g outputs remain high (open-circuit state), resulting in blanked display. This behavior prevents erroneous digit rendering and is inherent to the device's internal decoding logic.

Is SN7447AN RoHS compliant?

Yes, SN7447AN is RoHS compliant, with lead finish specified as NiPdAu (NIPDAU) and fully compliant with EU Directive 2011/65/EU. The part marking "SN7447AN" appears on the package body, and it ships in tube packaging with 25 units per tube.

How does the lamp test (LT̅) function work on SN7447AN?

When LT̅ is pulled low (≤0.8 V), SN7447AN overrides all BCD inputs and forces all segment outputs (a–g) low simultaneously, illuminating all seven segments regardless of input state. This provides immediate visual verification of LED continuity and wiring integrity during manufacturing or maintenance.