Texas Instruments CD40147BEG4

Overview

CD40147BEG4 from Texas Instruments is a CMOS 10-line-to-4-line priority encoder IC that converts active-high decimal inputs (0–9) into active-low BCD outputs (8, 4, 2, 1), with line 9 assigned highest priority. It operates over –55°C to +125°C, features buffered TTL-compatible outputs (driving one LSTTL load), and outputs all-high (VSS) when no input is asserted. Used in keyboard encoding and digital control panels requiring priority resolution.

For engineers reviewing the CD40147BEG4 datasheet, CD40147BEG4 pinout, CD40147BEG4 application, or CD40147BEG4 equivalent, key selection considerations include priority encoding behavior, active-low BCD output polarity, PDIP-16 package compatibility, and direct functional alignment with TTL 74147 when pin 15 is grounded.

Technical Context

The CD40147BEG4 implements combinational priority logic where only the highest-numbered asserted input (0–9) determines the BCD output; lower-priority inputs are masked. Its internal structure uses NAND-based decoding with active-low outputs and open-drain-compatible drive capability.

All ten inputs are individually buffered, and the four BCD outputs are actively driven low or pulled high via internal pull-ups to VSS - not VDD - resulting in true active-low logic levels. Input thresholds are CMOS-compatible (V_IL ≤ 0.3V_DD, V_IH ≥ 0.7V_DD), ensuring noise immunity across supply voltages from 3V to 18V.

Key Specifications

Pinout & Package

CD40147BEG4 is supplied in a 16-pin plastic dual-in-line package (PDIP-N), with 0.3-inch body width and through-hole mounting. Pin spacing is 0.1 inch; lead finish is NiPdAu (NIPDAU).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar priority encoder applications.

Compared with CD40147BM and SN74LS147N, the CD40147BEG4 uniquely combines through-hole PDIP packaging, 3–18V operation, and guaranteed priority encoding - making it the sole option for ruggedized, multi-voltage, hand-soldered, or legacy-replacement use cases.

Availability

CD40147BEG4 is available at Aetrix Electronics and suitable for keyboard interfaces, industrial control panels, legacy system upgrades, and test equipment selectors requiring stable component supply and long-lifecycle availability.

Supply support for CD40147BEG4 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 CD40147BEG4 belongs to TI's legacy CMOS logic portfolio, designed specifically for robust, wide-supply-voltage digital encoding in harsh environments and long-lifecycle industrial systems.

FAQ

What is the function of pin 15 on the CD40147BEG4?

Pin 15 on the CD40147BEG4 is the enable input. When tied low (VSS), the CD40147BEG4 operates normally as a priority encoder. Leaving it floating or high disables encoding - all outputs remain high. This pin allows functional alignment with TTL 74147, which lacks an enable but shares identical truth table behavior when pin 15 is grounded.

Does the CD40147BEG4 support 3.3V logic systems?

Yes, the CD40147BEG4 supports 3.3V operation within its specified 3V to 18V supply range. Input thresholds scale with VDD (V_IL ≤ 0.3V_DD, V_IH ≥ 0.7V_DD), so at 3.3V, valid logic low is ≤0.99V and logic high is ≥2.31V - compatible with standard 3.3V CMOS and LVTTL outputs.

How does the CD40147BEG4 handle simultaneous input assertions?

The CD40147BEG4 resolves simultaneous input assertions using hardwired priority logic: only the highest-numbered active input (I9 > I8 > … > I0) determines the BCD output. Lower-priority inputs are fully masked - no arbitration delay or metastability occurs, ensuring deterministic, glitch-free encoding critical for real-time control.

Is the CD40147BEG4 pin-compatible with the SN74HC147?

No, the CD40147BEG4 is not pin-compatible with SN74HC147. While both are 10-to-4 priority encoders, SN74HC147 uses active-low inputs and active-high outputs, whereas CD40147BEG4 uses active-high inputs and active-low outputs. Their pinouts differ: SN74HC147 places VCC at pin 16 and GND at pin 8, opposite to CD40147BEG4's VDD (pin 16) and VSS (pin 8) arrangement.

What is the maximum output sink current per pin on the CD40147BEG4?

The CD40147BEG4 output stage is rated to drive one low-power Schottky TTL load, defined as 0.4mA sink current at VO = 0.4V (VDD = 5V). At higher supply voltages (e.g., 12V), sink capability increases slightly due to higher internal drive strength, but design margin should maintain ≤0.4mA for guaranteed TTL compatibility and thermal safety.