Texas Instruments CD4055BM

Overview

CD4055BM from Texas Instruments is a CMOS BCD-to-7-segment latch/decoder/driver IC designed for direct LED display interfacing. It accepts 4-bit binary-coded decimal input, latches data, decodes to seven-segment outputs (a–g), and drives common-anode LED displays with sink-current capability. Key specs include 3–18 V supply range, 100 µA max quiescent current, and −55°C to +125°C operating temperature.

For engineers reviewing the CD4055BM datasheet, CD4055BM pinout, CD4055BM application, or CD4055BM equivalent, this device is selected for low-power, direct-drive numeric display systems in industrial instrumentation, panel meters, and legacy control interfaces where TTL-compatible logic levels and latch functionality are required.

Technical Context

The CD4055BM implements a synchronous latch followed by a BCD-to-7-segment decoder with active-low segment outputs optimized for common-anode LEDs. Its internal latch holds input data until updated, eliminating need for external storage in static display applications.

Unlike the CD4056B (which features TTL-compatible inputs and higher drive strength), the CD4055BM uses standard CMOS input thresholds and provides segment outputs rated for 1.5 mA sink current at V_DD = 5 V, with output voltage swing limited to V_DD − 0.5 V (min) under load.

Key Specifications

Pinout & Package

CD4055BM is supplied in a 16-pin SOIC (D) package with 3.9 mm body width, 1.2 mm max height, and 0.65 mm lead pitch per JEDEC MO-153.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD4056BM and MC14495P, the CD4055BM uniquely combines CMOS input compatibility, lamp test functionality, and 3–18 V operation-making it optimal for new designs requiring flexibility, diagnostics, and broad environmental tolerance.

Availability

CD4055BM is available at Aetrix Electronics and suitable for industrial panel meters, legacy instrumentation displays, and automotive dashboard indicators requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for CD4055BM 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 emphasis on industrial, automotive, and aerospace reliability.

The CD4000-series CMOS logic family-including CD4055BM-was engineered for low-power, high-noise-immunity digital interfacing in harsh environments, particularly targeting display, control, and instrumentation subsystems.

FAQ

What is the primary function of the CD4055BM?

The CD4055BM is a CMOS BCD-to-7-segment latch/decoder/driver IC. It accepts a 4-bit BCD input, latches the data on a rising LE edge, decodes it into seven active-low segment outputs (a–g), and directly drives common-anode LED displays. Its design integrates latch, decode, and drive functions in one 16-pin SOIC package, simplifying static numeric display implementations.

Does the CD4055BM support common-cathode LED displays?

No, the CD4055BM does not support common-cathode LED displays. Its segment outputs (pins 6–7, 9–13) are active-low and designed to sink current into the anodes of common-anode displays. Driving common-cathode displays would require external inverters or high-side drivers, which are not supported by the CD4055BM's output structure or specification.

What is the purpose of the BL and LT pins on the CD4055BM?

The BL (Blanking) pin is active-low and forces all segment outputs high to turn off the display regardless of latch content. The LT (Lamp Test) pin is also active-low and forces all segment outputs low to illuminate every segment simultaneously for visual verification. Both are independent control inputs that operate asynchronously with respect to the latch enable signal.

Can the CD4055BM operate from a 3.3 V supply?

Yes, the CD4055BM supports a supply voltage range of 3 V to 18 V. At 3.3 V, its segment outputs deliver approximately 0.3 mA sink current (per TI datasheet curves), sufficient for low-brightness or high-efficiency LED segments. Input thresholds scale with V_DD, so 3.3 V logic sources interface directly without level shifting.

Is the CD4055BM pin-compatible with the CD4056BM?

Yes, the CD4055BM and CD4056BM share identical pinouts and package footprints (16-pin SOIC, D package). However, their input thresholds and segment drive strengths differ: CD4055BM uses standard CMOS thresholds and 1.5 mA drive, while CD4056BM uses TTL-compatible thresholds and 2.5 mA drive. Functional substitution requires verifying source logic family and LED current requirements.