Texas Instruments CD4556BM

Overview

CD4556BM from Texas Instruments is a dual 1-of-4 decoder/demultiplexer IC in SOIC-16 package, operating across -55°C to +125°C, with supply voltage range 3 V to 18 V, and typical propagation delay of 120 ns at 10 V. It serves as a logic-level address decoder in industrial control panels requiring high-voltage tolerance and wide temperature operation.

For engineers reviewing the CD4556BM datasheet, CD4556BM pinout, CD4556BM application, or CD4556BM equivalent, key selection criteria include its dual independent decode function, CMOS-compatible input thresholds, TTL/CMOS interfacing capability, and compatibility with legacy 4000-series logic families in mixed-voltage systems.

Technical Context

The CD4556BM implements two identical 1-of-4 decoders, each accepting two binary inputs (A0/A1) and enabling via separate active-high enable pins (E1/E2). Each decoder drives four mutually exclusive outputs (Y0–Y3), with outputs low when enabled and matching input code, and high-impedance when disabled.

It uses standard CMOS silicon-gate technology, delivering rail-to-rail output swing, static immunity up to ±2 kV HBM, and no internal pull-ups-outputs require external termination for wired-OR or bus applications. Input hysteresis is not specified; inputs are compatible with TTL, CMOS, and high-impedance microcontroller GPIOs.

Key Specifications

Pinout & Package

CD4556BM is housed in a 16-pin SOIC (D) package per JEDEC MS-012, 7.5 mm body width, 1.75 mm max height, with 1.27 mm pitch and gull-wing leads. Pin 1 is marked by a beveled corner or laser dot; device orientation follows standard SOP quadrant Q1 tape feed.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual 1-of-4 decoder applications.

Compared with CD4556BE and MC14556B, the CD4556BM offers surface-mount efficiency and RoHS compliance in a compact SOIC-16, while retaining full functional equivalence and extended temperature support - making it optimal for new industrial PCB designs prioritizing density and automated assembly.

Availability

CD4556BM is available at Aetrix Electronics and suitable for industrial control systems, automotive sensor interfaces, and legacy system upgrades requiring stable component supply and long-lifecycle support.

Supply support for CD4556BM 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 90 years of innovation in industrial, automotive, and aerospace electronics.

The CD4556BM belongs to TI's legacy 4000-series CMOS logic family, designed for robust, wide-supply-voltage digital interfacing in harsh-environment applications where reliability and longevity outweigh speed-critical requirements.

FAQ

What is the maximum clock or address transition frequency supported by CD4556BM?

The CD4556BM is not a clocked device and has no maximum frequency rating. Its operation depends on input setup/hold times and propagation delay: with 120 ns typical delay at 10 V, it supports reliable decoding of address transitions up to approximately 4 MHz in worst-case combinatorial paths. For CD4556BM, design margins should maintain ≥200 ns between successive address changes to ensure glitch-free output selection.

Can CD4556BM drive LEDs directly without current-limiting resistors?

No, CD4556BM outputs are not designed for direct LED driving. Its ±4.2 mA output drive at 10 V is rated for logic loading only; connecting an LED directly risks exceeding absolute maximum output current and damaging the output stage. For CD4556BM, always use a series current-limiting resistor - e.g., 1 kΩ for a 5 V supply and red LED - or buffer with a transistor if higher current is needed.

Is CD4556BM pin-compatible with the CD4555B decoder?

No, CD4556BM is not pin-compatible with CD4555B. While both are 16-pin SOIC decoders, CD4555B is a dual 1-of-8 decoder with three inputs per section (A0–A2) and eight outputs, whereas CD4556BM is a dual 1-of-4 decoder with two inputs (A0/A1) and four outputs per section. Their pinouts differ significantly - for example, CD4555B dedicates pins 1–3 to A0–A2 of decoder 1, while CD4556BM uses pins 1–2 for A0/A1 and pin 3 for E1.

Does CD4556BM support mixed-voltage operation - e.g., 5 V inputs with 12 V VDD?

Yes, CD4556BM supports mixed-voltage operation: inputs are fully compatible with 5 V TTL/CMOS logic even when VDD = 12 V, due to its voltage-independent input threshold (≈0.5×VDD). For CD4556BM, a 2.5 V input high is sufficient at 12 V VDD, well within 5 V logic high levels. No level shifters are needed, simplifying interface design between 3.3 V/5 V controllers and 12 V peripheral rails.

What is the recommended PCB layout practice for CD4556BM in high-noise industrial environments?

For CD4556BM, place a 0.1 µF X7R ceramic capacitor between VDD (pin 16) and VSS (pin 8) as close as possible to the device - ideally within 3 mm - to suppress supply transients. Route input traces away from noisy power or relay traces, and avoid running them parallel to clock lines. Ground the exposed pad (if present - though SOIC-D lacks thermal pad) and use solid ground pour beneath the IC to minimize impedance. These practices reduce susceptibility to fast-edge noise coupling into CD4556BM's high-impedance CMOS inputs.