Texas Instruments SN74LS247NSR

Overview

SN74LS247NSR from Texas Instruments is a 7-segment BCD-to-7-segment decoder/driver IC designed for direct interface to common-anode LED displays. It features active-low outputs, lamp test (LT̅), ripple blanking input (RB̅), and blanking input (BI̅), operates from 4.75 V to 5.25 V, supports 0°C to 70°C ambient, and drives up to 40 mA per segment in sink configuration. It is used in digital panel meters and industrial display systems.

For engineers reviewing the SN74LS247NSR datasheet, SN74LS247NSR pinout, SN74LS247NSR application, or SN74LS247NSR equivalent, key selection considerations include its active-low open-collector output architecture, common-anode LED compatibility, TTL-level input thresholds, and absence of internal current limiting - requiring external series resistors for segment current control.

Technical Context

The SN74LS247NSR implements combinational logic decoding of 4-bit binary-coded decimal (BCD) inputs (A0–A3) into seven active-low outputs (a–g) for driving common-anode 7-segment displays. Its internal logic includes priority encoding for blanking functions: BI̅ overrides LT̅ and RB̅, while RB̅ enables cascading for leading-zero suppression across multi-digit displays.

It uses standard TTL circuitry with Schottky-clamped transistors, delivering typical propagation delays of 30 ns (max 45 ns) at VCC = 5 V and TA = 25°C. Input clamp diodes allow handling of negative transient voltages down to –1.5 V, and output saturation voltage is specified at ≤ 0.5 V when sinking 40 mA.

Key Specifications

Pinout & Package

SOP (NS) package - 16-pin small-outline plastic package with 1.27 mm lead pitch, 8.45 mm body width, 10.55 mm body length, and 2.00 mm max height. Compliant with JEDEC MS-012, RoHS-compliant NIPDAU lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-7-segment decoder/driver applications.

Compared with SN74LS247NSR, SN74LS47DR offers identical electrical and functional behavior in a different package variant, while SN74LS248N provides complementary output polarity for alternate display architectures - neither is pin-compatible without layout adaptation, but both serve equivalent system-level decoding roles.

Availability

SN74LS247NSR is available at Aetrix Electronics and suitable for industrial panel meters, digital clock displays, and test equipment counters requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS247NSR 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 SN74LS247NSR belongs to TI's legacy 74LS logic family, engineered specifically for reliable BCD-driven LED display interfaces in commercial-grade instrumentation and control systems.

FAQ

What is the output configuration of the SN74LS247NSR?

The SN74LS247NSR features active-low open-collector outputs designed exclusively for common-anode LED displays. Each segment output (a–g) sinks current when asserted; external pull-up resistors or LED anodes must be connected to VCC. It does not include internal current-limiting resistors, so external series resistors are mandatory to limit segment current to ≤40 mA.

Can the SN74LS247NSR drive common-cathode displays?

No, the SN74LS247NSR cannot directly drive common-cathode displays because its outputs are active-low and open-collector - they sink current to ground and require the LED anode to be tied to VCC. For common-cathode displays, use SN74LS248N instead, which provides active-high outputs compatible with cathode-grounded LEDs.

What is the purpose of the RB̅ (Ripple Blanking Input) pin on the SN74LS247NSR?

The RB̅ pin on the SN74LS247NSR enables leading-zero suppression in multi-digit displays. When asserted low, it blanks the current digit if all inputs are zero and propagates a blanking signal (via RBO̅) to the next stage. This allows cascading multiple SN74LS247NSR devices to display " 123" instead of "0123", improving readability and reducing unnecessary LED power consumption.

Does the SN74LS247NSR require external current-limiting resistors?

Yes, the SN74LS247NSR requires external series current-limiting resistors on each segment output. Its open-collector outputs lack internal current regulation, and maximum sink current per output is 40 mA. Resistor values must be selected based on LED forward voltage and desired brightness - for example, a 150 Ω resistor limits current to ~23 mA with a 1.8 V red LED at 5 V VCC.

Is the SN74LS247NSR compatible with modern microcontrollers?

Yes, the SN74LS247NSR is compatible with modern microcontrollers that provide TTL-level outputs (e.g., 3.3 V logic with appropriate buffer or level shifter). Its inputs meet standard LS-TTL thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V), so direct connection is possible from 5 V MCUs; for 3.3 V MCUs, a simple transistor or buffer may be needed to ensure reliable high-level recognition.