Texas Instruments SN7445NSR

Overview

SN7445NSR from Texas Instruments is a 16-pin BCD-to-7-segment decoder/driver IC designed for direct LED display interfacing in digital instrumentation and control panels. It features active-low open-collector outputs, TTL-compatible inputs, 30 mA per segment sink capability, and operates over 0°C to 70°C. It drives common-anode 7-segment displays without external current-limiting resistors in many configurations.

For engineers reviewing the SN7445NSR datasheet, SN7445NSR pinout, SN7445NSR application, or SN7445NSR equivalent, key selection criteria include its open-collector output architecture, BCD input decoding logic, segment drive strength, thermal operating range, and compatibility with standard 7-segment LED displays in industrial panel meters and legacy digital readouts.

Technical Context

The SN7445NSR implements a fixed BCD-to-7-segment decoding function with active-low outputs mapped to segments a–g and decimal point (DP). Its internal logic directly converts 4-bit binary-coded decimal inputs into seven complementary output signals that sink current to illuminate common-anode LED segments.

It uses standard TTL input thresholds and provides open-collector outputs rated for 30 mA DC per segment at V_CC = 5 V, enabling direct connection to LEDs with minimal external components. No internal current limiting or latch functionality is present - it operates purely as a combinational decoder/driver.

Key Specifications

Pinout & Package

SN7445NSR is housed in a 16-pin plastic dual in-line package (PDIP-N), 0.3-inch body width, with standard through-hole lead spacing and RoHS-compliant NiPdAu plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS47N and MC14495P, the SN7445NSR uniquely combines high-current open-collector outputs with full hardware blanking and lamp-test support in a TTL-compatible 16-pin PDIP, making it optimal for standalone, direct-drive 7-segment systems requiring diagnostic flexibility and robust segment illumination.

Availability

SN7445NSR is available at Aetrix Electronics and suitable for digital instrumentation, industrial control displays, and legacy equipment retrofits requiring stable component supply and long-term obsolescence management.

Supply support for SN7445NSR 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 for industrial, automotive, and communications markets.

The SN7445NSR belongs to TI's legacy 74xx TTL logic family, engineered specifically for reliable BCD-to-7-segment translation in cost-sensitive, through-hole-based digital display systems.

FAQ

What is the maximum output current per segment on the SN7445NSR?

The SN7445NSR provides up to 30 mA DC sink current per segment output (pins 3, 4, 5, 9, 10, 11, 15) when V_CC = 5 V and ambient temperature is within 0°C to 70°C. This rating allows direct driving of common-anode LEDs without external current-limiting resistors in many static or low-duty-cycle applications. Exceeding this current risks thermal overstress or output degradation in the SN7445NSR.

Does the SN7445NSR support multi-digit display blanking?

Yes, the SN7445NSR supports multi-digit blanking via its BI̅/RBO̅ pin (pin 14), which functions as both blanking input and ripple blanking output. When used in cascaded configurations, the RBO̅ output of a more-significant digit asserts BI̅ on the next-lower digit to suppress leading zeros - a feature confirmed in TI's SN7445 datasheet and essential for clean numeric formatting in instruments using the SN7445NSR.

Is the SN7445NSR pin-compatible with the SN74LS47N?

Yes, the SN7445NSR is pin-compatible with the SN74LS47N: both use 16-pin PDIP packages with identical pin assignments for BCD inputs (A0–A3), segment outputs (a–g), V_CC, GND, and control pins (LT̅, RBI, BI̅/RBO̅). However, the SN7445NSR delivers significantly higher output current (30 mA vs. 2.4 mA), enabling direct LED drive where SN74LS47N would require external drivers.

What is the purpose of the LT̅ (Lamp Test) input on the SN7445NSR?

The LT̅ (pin 13) input on the SN7445NSR forces all seven segment outputs low when asserted, regardless of BCD input state. This enables hardware-level verification of LED continuity and display wiring integrity without modifying input data - a critical diagnostic function supported natively in the SN7445NSR and widely used during manufacturing test and field service of digital readouts.

Can the SN7445NSR operate from a 3.3 V supply?

No, the SN7445NSR is specified only for 4.75 V to 5.25 V operation. Its TTL-compatible input thresholds and open-collector output structure require a nominal 5 V supply to meet guaranteed switching levels and output current ratings. Operating the SN7445NSR at 3.3 V will result in undefined logic states, insufficient output drive, and potential functional failure - it is not 3.3 V compatible.