Texas Instruments SN74LS47NSR

Overview

SN74LS47NSR from Texas Instruments is a TTL 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/ripple blanking output (BI̅/RBO̅), and operates over 0°C to 70°C with V_CC = 4.75 V to 5.25 V.

For engineers reviewing the SN74LS47NSR datasheet, SN74LS47NSR pinout, SN74LS47NSR application, or SN74LS47NSR equivalent, key selection considerations include its active-low open-collector outputs for common-anode LED drive, built-in leading/trailing zero suppression via BI̅/RBO̅ and RBI̅, TTL-compatible input thresholds, and SOP-16 packaging for surface-mount compatibility in legacy digital panel designs.

Technical Context

The SN74LS47NSR implements combinational logic decoding of 4-bit BCD inputs (A–D) into seven active-low segment outputs (a–g) that directly sink current to drive common-anode LEDs. Its internal logic incorporates priority encoding for blanking control: BI̅ forces all outputs high when asserted, while RBI̅ enables zero-suppression cascading via RBO̅ when all inputs are low and LT̅ is inactive.

Unlike CMOS variants, the SN74LS47NSR uses bipolar TTL circuitry with guaranteed output sink current ≥ 24 mA per segment at V_OL ≤ 0.5 V, supports wired-OR interconnection via open-collector outputs, and requires external current-limiting resistors for LED anodes. It does not include internal current regulation or latch functionality.

Key Specifications

Pinout & Package

SOP-16 (NS) package: 10.4 mm × 5.3 mm body, 2.00 mm max height, 1.27 mm lead pitch, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.

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 SN74LS48N, the SN74LS47NSR offers surface-mount compatibility without altering logic behavior or timing - making it optimal for new SMT production runs while maintaining full functional equivalence to through-hole variants in common-anode systems.

Availability

SN74LS47NSR is available at Aetrix Electronics and suitable for digital panel meters, industrial HMIs, legacy test equipment upgrades, and automotive dashboard prototypes requiring stable component supply across long-lifecycle programs.

Supply support for SN74LS47NSR 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 applications.

The SN74LS47NSR belongs to TI's legacy 74LS logic family, engineered for robust TTL-level interfacing in fixed-function digital display subsystems where low-cost, predictable timing, and hardware-based zero suppression are critical.

FAQ

What is the maximum sink current per segment output on the SN74LS47NSR?

The SN74LS47NSR guarantees a minimum output sink current of 24 mA per segment (pins a–g) at V_OL ≤ 0.5 V under V_CC = 5 V and T_A = 25°C. This allows direct drive of standard 20 mA LED segments with appropriate anode-side current-limiting resistors. Exceeding 24 mA risks exceeding absolute maximum ratings and may degrade long-term reliability of the SN74LS47NSR.

Can the SN74LS47NSR drive common-cathode LED displays?

No, the SN74LS47NSR cannot directly drive common-cathode LED displays. Its segment outputs are active-low open-collector - designed exclusively for sinking current from common-anode LED anodes. To drive common-cathode displays, use the functionally identical but output-polarity-inverted SN74LS48N or SN74LS48NSR instead. Attempting to use SN74LS47NSR with common-cathode LEDs results in no illumination or incorrect segment activation.

How does zero suppression work on the SN74LS47NSR?

Zero suppression on the SN74LS47NSR uses the BI̅/RBO̅ and RBI̅ pins to blank leading or trailing zeros in multi-digit displays. When RBI̅ is low and all BCD inputs (A–D) are low, the SN74LS47NSR asserts RBO̅ low - signaling upstream/downstream SN74LS47NSR devices to blank their outputs. This cascaded behavior enables automatic suppression of unnecessary zeros (e.g., "0042" displays as " 42") without microcontroller intervention.

Is the SN74LS47NSR RoHS compliant?

Yes, the SN74LS47NSR is RoHS compliant, with NiPdAu (nickel-palladium-gold) lead finish and compliance verified per EU Directive 2011/65/EU. The "Yes" RoHS designation in TI's packaging documentation confirms full conformance, including restrictions on lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE. This makes the SN74LS47NSR suitable for commercial electronics sold in EU and other regulated markets.

What is the recommended current-limiting resistor value for SN74LS47NSR-driven LEDs?

For standard 2.0 V red LEDs at 15 mA segment current with V_CC = 5 V, use a 200 Ω resistor between each LED anode and V_CC. Calculation: R = (5.0 V − 2.0 V) / 0.015 A = 200 Ω. This stays within the SN74LS47NSR's 24 mA per-segment limit while ensuring consistent brightness and thermal margin. Always verify LED forward voltage and desired current against the specific SN74LS47NSR output voltage drop (≤0.5 V) and ambient temperature conditions.