Texas Instruments CD4056BE

Overview

CD4056BE from Texas Instruments is a CMOS BCD-to-7-segment latch/decoder/driver IC designed for direct LED display interfacing. It accepts 4-bit BCD input, latches data, decodes to seven-segment outputs (a–g), and drives common-cathode LED displays with sink-current capability up to 1.5 mA per segment at V_DD = 15 V. It operates across –55°C to +125°C and features TTL-compatible inputs.

For engineers reviewing the CD4056BE datasheet, CD4056BE pinout, CD4056BE application, or CD4056BE equivalent, key selection considerations include its BCD latching behavior, common-cathode output polarity, segment current drive limits, wide supply range (3 V to 18 V), and compatibility with legacy 4000-series logic timing and voltage levels.

Technical Context

The CD4056BE integrates a 4-bit D-type latch, BCD-to-7-segment decoder, and seven open-drain N-channel MOSFET output drivers - each capable of sinking current to drive common-cathode LEDs directly. Its latch enables synchronous data capture on the LE (Latch Enable) input, isolating display updates from input changes.

It uses standard CMOS circuitry with buffered inputs, high noise immunity (>50% V_DD), and rail-to-rail output swing. Unlike the CD4054B (common-anode driver) or CD4055B (non-latching decoder), the CD4056BE includes both latching and decoding in one package, eliminating external latch requirements in static display systems.

Key Specifications

Pinout & Package

CD4056BE is supplied in a 16-pin plastic dual-in-line package (PDIP-N), 19.1 mm × 6.6 mm body size, 2.54 mm lead pitch, through-hole mounting compatible with standard 0.1″ grid PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD4511BE and MC14495P, the CD4056BE uniquely combines latching, common-cathode drive, and blanking/test controls in a single 16-pin package - making it optimal for cost-sensitive, space-constrained, or legacy-compatible LED display subsystems requiring minimal external components.

Availability

CD4056BE is available at Aetrix Electronics and suitable for industrial panel meters, test equipment displays, and legacy instrumentation upgrades requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD4056BE 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 global semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and aerospace qualification.

The CD4056BE belongs to TI's legacy 4000-series CMOS logic family, designed specifically for low-power, high-noise-immunity digital display interfacing in harsh environments where reliability and voltage flexibility are critical.

FAQ

What is the primary function of the CD4056BE?

The CD4056BE is a BCD-to-7-segment latch/decoder/driver IC that accepts 4-bit binary-coded decimal input, stores it in an internal D-latch, decodes it into seven segment signals (a–g), and drives common-cathode LED displays via open-drain N-channel outputs. Its integrated latch eliminates the need for external storage, making the CD4056BE ideal for stable, low-glitch display updates in industrial and instrumentation applications.

Can the CD4056BE drive common-anode LED displays?

No, the CD4056BE cannot directly drive common-anode LED displays. Its outputs are open-drain N-channel MOSFETs designed to sink current from LED anodes tied to V_DD, meaning it is strictly for common-cathode configurations. Attempting to use the CD4056BE with common-anode displays would result in no illumination or incorrect segment activation. For common-anode applications, consider the CD4511BE instead.

What is the purpose of the Lamp Test (LT) pin on the CD4056BE?

The Lamp Test (LT) pin on the CD4056BE is an active-low control that, when pulled low, forces all seven segment outputs (a–g) into high-impedance (off) state - effectively turning off all LEDs. When LT is high, normal decoding and driving resume. This feature allows quick visual verification of LED continuity and segment wiring integrity during manufacturing or field service without modifying software or BCD input.

Does the CD4056BE require external pull-up resistors on its segment outputs?

Yes, the CD4056BE requires external pull-up resistors on all segment outputs (pins 8–14) because they are open-drain N-channel MOSFETs. These resistors connect each segment output to V_DD (or a separate LED supply rail) and set the LED current magnitude. Typical values range from 1 kΩ to 10 kΩ depending on V_DD, LED forward voltage, and desired brightness - ensuring the CD4056BE stays within its 1.5 mA per-output sink limit.

Is the CD4056BE compatible with modern microcontrollers operating at 3.3 V logic levels?

Yes, the CD4056BE is compatible with 3.3 V microcontrollers when powered at V_DD ≥ 3 V. Its TTL-compatible inputs recognize voltages ≥ 0.7×V_DD as high, so at V_DD = 3.3 V, a 3.3 V GPIO output meets the high-threshold requirement. However, ensure the microcontroller's output high voltage does not exceed V_DD of the CD4056BE to avoid overstress - use series resistors if interfacing with 5 V or higher logic.