Texas Instruments CD4028BM

Overview

CD4028BM from Texas Instruments is a BCD-to-decimal decoder/driver IC in a 16-pin SOIC (D) package, operating across -55°C to +125°C, with TTL-compatible input thresholds and CMOS-level output drive capability. It converts 4-bit binary-coded decimal inputs into ten active-high decimal outputs, enabling direct LED or relay interface in industrial control panels and digital instrumentation.

For engineers reviewing the CD4028BM datasheet, CD4028BM pinout, CD4028BM application, or CD4028BM equivalent, key selection considerations include its BCD decoding logic, high-noise-immunity CMOS inputs, rail-to-rail output swing, and compatibility with legacy 4000-series logic families in low-power, wide-temperature embedded systems.

Technical Context

The CD4028BM implements combinational logic using standard CMOS process technology, with all inputs buffered by Schmitt-trigger-like hysteresis for noise rejection. Its internal architecture consists of NAND/NOR gates configured to decode only valid BCD codes (0000–1001), leaving outputs 10–15 unasserted for invalid inputs.

It features symmetrical output drive strength (±4.2 mA at V_DD = 10 V), propagation delays under 100 ns (typical) across the full temperature range, and no internal latching-requiring external clocking or static input hold for stable output states.

Key Specifications

Pinout & Package

CD4028BM is housed in a 16-pin SOIC (D) package per JEDEC MS-012, 3.9 mm body width, 1.75 mm height max, with 1.27 mm pitch and gull-wing leads. Pin 1 is located at the top-left corner with notch or index mark.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-decimal decoding applications.

Compared with CD4028BM, CD4028BE offers through-hole reliability for lab-grade instruments, while CD4028BNSR provides identical performance in a mechanically distinct SOP variant - neither is pin-compatible without footprint revision, but all three share identical truth tables, timing, and DC characteristics.

Availability

CD4028BM is available at Aetrix Electronics and suitable for industrial control panels, test equipment front panels, and legacy instrumentation upgrades requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD4028BM 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 specializing in analog, embedded processing, and logic solutions, with over 50 years of CMOS logic innovation and industrial qualification expertise.

The CD4028BM belongs to TI's legacy 4000B-series CMOS logic family, designed for robust, low-power digital interfacing in harsh environments where reliability, wide voltage operation, and temperature resilience are critical.

FAQ

What is the logic function of the CD4028BM?

The CD4028BM is a BCD-to-decimal decoder that accepts a 4-bit binary-coded decimal input (A–D, with A as LSB) and asserts exactly one of ten active-high outputs (0–9) corresponding to the decimal value. It ignores invalid BCD codes (10–15), ensuring no false outputs. This behavior is fixed in silicon and requires no configuration or programming - the CD4028BM performs pure combinational decoding with no internal memory or state.

Does the CD4028BM support 5-V or 3.3-V operation?

Yes, the CD4028BM operates over a continuous supply range of 3 V to 18 V, making it fully compatible with both 5-V and 3.3-V systems. At V_DD = 3.3 V, input thresholds scale accordingly (V_IH ≈ 2.3 V, V_IL ≈ 1.0 V), and output drive remains functional - though output current drops to approximately ±1.5 mA. The CD4028BM does not require level shifters when interfacing with 3.3-V microcontrollers or 5-V peripherals.

Can the CD4028BM drive LEDs directly?

Yes, each output of the CD4028BM can source or sink up to ±4.2 mA at V_DD = 10 V, which is sufficient to drive standard low-current LEDs (e.g., 2 mA @ 2 V forward drop) with a series resistor. For example, with V_DD = 5 V and a red LED (V_F = 1.8 V), a 1.0 kΩ resistor limits current to ~3.2 mA - well within CD4028BM specifications. No external transistor is needed unless higher current or AC-coupled loads are required.

Is the CD4028BM pin-compatible with the 74LS42?

No, the CD4028BM is not pin-compatible with the 74LS42. While both perform BCD-to-decimal decoding, the 74LS42 uses active-low outputs and has different pin assignments (e.g., outputs Y0–Y9 occupy pins 1, 2, 3, 4, 5, 6, 7, 9, 10, 11), whereas the CD4028BM uses active-high outputs mapped to pins 3–5, 9–11, 13, and 14. Interchanging them requires PCB redesign and logic inversion - the CD4028BM is a functional, not mechanical, alternative.

What is the maximum operating frequency for CD4028BM inputs?

The CD4028BM is a static combinational device with no clock input, so it has no defined "operating frequency" - instead, its speed is governed by propagation delay. With V_DD = 15 V and C_L = 50 pF, t_PLH/t_PHL is 80 ns max. To ensure clean output transitions, input changes should be stable for ≥100 ns before and after the transition point. Thus, reliable operation is achievable up to ~5 MHz in edge-triggered systems, but the CD4028BM itself imposes no periodic timing constraint beyond setup/hold timing margins.