Texas Instruments SN74LS248N

Overview

SN74LS248N from Texas Instruments is a 7-segment BCD-to-7-segment decoder/driver IC with active-low open-collector outputs, designed for direct interface to common-anode LED displays. It features TTL-compatible inputs, lamp test (LT̅), blanking (BI̅/RBO̅), and ripple-blanking input ( RBI̅ ), operating over 0°C to 70°C with typical propagation delay of 45 ns and supply current of 36 mA.

For engineers reviewing the SN74LS248N datasheet, SN74LS248N pinout, SN74LS248N application, or SN74LS248N equivalent, key selection considerations include its active-low output architecture, common-anode LED drive capability, built-in blanking and ripple-blanking logic, and PDIP-16 package compatibility with through-hole prototyping and legacy industrial control panels.

Technical Context

The SN74LS248N implements combinational logic that converts 4-bit binary-coded decimal (BCD) inputs (A0–A3) into seven active-low segment drive signals (a–g). Its internal logic includes priority encoding for blanking: BI̅/RBO̅ asserts low when all inputs are 0000 or when RBI̅ is low and outputs are zero, enabling cascaded multi-digit display blanking.

Unlike the SN74LS247, the SN74LS248N drives common-anode displays and includes an internal lamp test function (LT̅) that forces all segments high (i.e., turns on all LEDs) when asserted low - a feature confirmed in TI's official SN74LS248 datasheet and distinct from LS247's common-cathode orientation.

Key Specifications

Pinout & Package

SN74LS248N is supplied in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width, 0.1-inch lead pitch, and through-hole mounting configuration. The package meets JEDEC MS-001 and is RoHS-compliant with NiPdAu lead finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS247N and 74HC4511, the SN74LS248N uniquely combines TTL compatibility, common-anode drive, lamp test, and hardware ripple-blanking - making it irreplaceable in legacy 5 V systems requiring zero-software display management and leading-zero suppression.

Availability

SN74LS248N is available at Aetrix Electronics and suitable for digital panel meters, industrial control displays, legacy instrumentation, and education & lab trainer applications requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS248N 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 global manufacturing and quality certification.

The SN74LS248N belongs to TI's legacy 74LS logic family, engineered for reliability and interoperability in industrial, test, and educational equipment where deterministic TTL timing and through-hole serviceability remain critical.

FAQ

What is the primary function of the SN74LS248N?

The SN74LS248N is a BCD-to-7-segment decoder/driver IC optimized for common-anode LED displays. It accepts 4-bit BCD inputs (A0–A3) and produces active-low outputs (a–g) to illuminate corresponding segments. Its design includes lamp test (LT̅), blanking (BI̅/RBO̅), and ripple-blanking (RBI̅) functions - all documented in TI's official SN74LS248 datasheet. The SN74LS248N does not perform latching or scanning; it is purely combinational logic.

Can the SN74LS248N drive common-cathode displays?

No, the SN74LS248N cannot directly drive common-cathode displays. Its outputs are active-low open-collector, intended for sinking current into common-anode LED anodes. Driving a common-cathode display would require external inverters or PNP transistors - adding complexity and propagation delay. For common-cathode applications, TI specifies the SN74LS247N instead. The SN74LS248N's internal logic and output structure are fixed for common-anode use.

What is the purpose of the BI̅/RBO̅ pin on the SN74LS248N?

The BI̅/RBO̅ pin on the SN74LS248N serves dual roles: as Blanking Input (BI̅), it forces all segment outputs high (blanking the display) when pulled low; as Ripple-Blanking Output (RBO̅), it goes low only when the input BCD is 0000 *and* RBI̅ is low - enabling hardware-based suppression of leading zeros in multi-digit displays. This behavior is intrinsic to the SN74LS248N's internal logic and differs from SN74LS247N's implementation.

Is the SN74LS248N compatible with 3.3 V logic systems?

No, the SN74LS248N is not compatible with 3.3 V logic systems. It is a 74LS-family device requiring a nominal 5 V supply (4.75–5.25 V) and TTL-level inputs (VIH ≥ 2.0 V, VIL ≤ 0.8 V). Driving its inputs from 3.3 V logic may result in marginal or unreliable switching due to insufficient VIH margin. Interfacing with 3.3 V controllers requires level-shifting circuitry. The SN74LS248N is strictly a 5 V-only device.

Does the SN74LS248N include output latching?

No, the SN74LS248N does not include output latching. It is a purely combinational decoder: outputs change asynchronously with input changes, with propagation delay specified at 45 ns max. Latching functionality is absent in the SN74LS248N's architecture - unlike CMOS alternatives such as the 74HC4511. Any latching must be implemented externally using flip-flops or microcontroller firmware. This design choice ensures minimal latency and deterministic timing in the SN74LS248N.