Texas Instruments CD4056BM

Overview

CD4056BM from Texas Instruments is a BCD-to-7-segment latch/decoder/driver IC designed for direct LED display interfacing. It features active-high latch enable, TTL/CMOS-compatible inputs, 15 mA segment sink current per output, and operates across –55°C to +125°C. It drives common-cathode LED displays in industrial panel meters and instrumentation systems.

For engineers reviewing the CD4056BM datasheet, CD4056BM pinout, CD4056BM application, or CD4056BM equivalent, key selection considerations include its latch-controlled decoding function, high-current open-drain outputs, wide temperature range, and SOIC-16 packaging for space-constrained PCB layouts.

Technical Context

The CD4056BM integrates a 4-bit BCD input latch, binary-coded decimal decoder logic, and seven open-drain N-channel MOSFET drivers with built-in current-limiting capability. Its latch enables synchronous data capture before decoding, preventing display glitches during input transitions.

Each of the seven segment outputs (a–g) provides 15 mA sink current at V_DD = 15 V and V_SS = 0 V, supporting direct drive of low-voltage common-cathode LEDs without external current-limiting resistors in many configurations. Input thresholds are compatible with both TTL and CMOS logic families.

Key Specifications

Pinout & Package

CD4056BM is housed in a 16-pin SOIC (D) package with 1.27 mm lead pitch and 1.2 mm maximum height, optimized for automated assembly and thermal performance in dense layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD4056BM, CD4511BE offers simpler timing but lacks latch synchronization and lower drive strength, while MC14495P omits critical diagnostic controls and requires external components - making CD4056BM the optimal choice for robust, maintainable LED display subsystems requiring glitch immunity and field serviceability.

Availability

CD4056BM is available at Aetrix Electronics and suitable for industrial panel meters, test equipment displays, and automotive instrument clusters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD4056BM 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 leader delivering analog, embedded processing, and logic solutions with emphasis on reliability, longevity, and industrial-grade qualification.

The CD4056BM belongs to TI's legacy CMOS logic family, engineered specifically for robust LED display driving in harsh environments where latch stability, wide voltage operation, and diagnostic capability are critical.

FAQ

What is the primary function of the CD4056BM?

The CD4056BM is a BCD-to-7-segment latch/decoder/driver IC that converts 4-bit binary-coded decimal inputs into active-low signals for driving common-cathode LED displays. Its integrated latch prevents display glitches during input transitions, and its 15 mA per-segment sink current enables direct LED drive in many configurations. The CD4056BM is widely used in industrial and instrumentation applications where stable, high-brightness numeric readouts are required.

Does the CD4056BM support common-anode LED displays?

No, the CD4056BM is designed exclusively for common-cathode LED displays. Its seven segment outputs (a–g) are open-drain N-channel MOSFETs configured to sink current from LED anodes to ground. Driving common-anode displays would require external level-shifting circuitry or a different driver such as the CD4511BE. The CD4056BM's internal architecture and output polarity make it incompatible with direct common-anode connection.

What is the purpose of the Lamp Test (LT) and Blanking Input (BI) pins on the CD4056BM?

The Lamp Test (LT) pin, when pulled low, forces all segment outputs (a–g) low to illuminate every LED segment simultaneously - verifying LED continuity and driver health. The Blanking Input (BI), when pulled low, disables all segment outputs (driving them high) to turn off the display - enabling time-multiplexed multi-digit operation or display blanking. Both functions are integral to the CD4056BM's diagnostic and dynamic display control capabilities.

Can the CD4056BM operate from a 3.3 V supply?

Yes, the CD4056BM is fully specified to operate from 3 V to 18 V, including 3.3 V nominal supplies. At 3.3 V, its output sink current drops to approximately 1.5 mA per segment (per TI datasheet curves), which is sufficient to drive low-current indicator LEDs or high-efficiency red/green segments. For full 15 mA drive, ≥12 V is recommended. System designers must verify LED forward voltage and desired brightness at 3.3 V when using the CD4056BM.

Is the CD4056BM pin-compatible with the CD4511BE?

No, the CD4056BM and CD4511BE are not pin-compatible. While both are 16-pin BCD-to-7-segment drivers, their pin assignments differ significantly: CD4056BM places latch enable (LE) on pin 1 and blanking (BI) on pin 15, whereas CD4511BE uses pin 5 for latch enable and has no dedicated blanking input. Substituting one for the other requires PCB redesign. The CD4056BM's SOIC-16 (D) package also differs physically from CD4511BE's typical PDIP-16 footprint.