Texas Instruments CD74HCT4543EE4

Overview

CD74HCT4543EE4 from Texas Instruments is a BCD-to-7-segment latch/decoder/driver IC designed for direct driving of liquid-crystal displays (LCDs), featuring active-high latch enable (LD), blanking input (BI), and phase input (PH) for AC-coupled LCD backplane biasing. It operates from 4.5 V to 5.5 V, supports LSTTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2 V), and delivers balanced propagation delays (≤120 ns at 4.5 V, CL = 50 pF).

For engineers reviewing the CD74HCT4543EE4 datasheet, CD74HCT4543EE4 pinout, CD74HCT4543EE4 application, or CD74HCT4543EE4 equivalent, key selection considerations include its integrated latch function for static BCD code storage, PH-driven complementing outputs for LCD duty-cycle control, BI-enabled display blanking, and compatibility with common-anode or common-cathode 7-segment displays via external driver configuration.

Technical Context

The CD74HCT4543EE4 implements a three-stage architecture: input latches synchronized to LD, a BCD-to-7-segment decoder with active-low outputs, and segment drivers capable of sourcing/sinking up to 4 mA per output. Its PH input accepts a square wave (GND-to-VCC) that inverts all segment outputs on each transition - essential for preventing DC bias in LCDs.

Latch operation is edge-triggered: when LD is low, BCD inputs (D0–D3) are transparently latched; when LD is high, outputs reflect current inputs. BI forces all outputs low (blanking), independent of LD state. The device uses silicon-gate CMOS technology, achieving significant power reduction versus legacy LSTTL while maintaining direct logic-level compatibility.

Key Specifications

Pinout & Package

CD74HCT4543EE4 is housed in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and standard through-hole mounting. Pin 1 is located at the top-left corner (notch side left), and pin numbering proceeds counter-clockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS47N and CD4543BE, the CD74HCT4543EE4 uniquely combines LSTTL compatibility, integrated LCD bias control (PH), hardware blanking (BI), and low-power CMOS efficiency - making it the only choice for robust, single-chip BCD-driven LCD instrumentation within 5 V systems.

Availability

CD74HCT4543EE4 is available at Aetrix Electronics and suitable for industrial panel meters, automotive instrument clusters, test equipment, and medical device displays requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT4543EE4 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 communications markets.

The CD74HCT4543EE4 belongs to TI's HCT logic family - engineered for pin-for-pin compatibility with legacy TTL while delivering CMOS power efficiency and enhanced noise immunity for display interface applications.

FAQ

What is the primary function of the PH pin on the CD74HCT4543EE4?

The PH (Phase) pin on the CD74HCT4543EE4 accepts a square-wave input (GND to VCC) that synchronously complements all seven segment outputs (a–g). This AC-coupling feature eliminates DC voltage across LCD segments, preventing electrochemical degradation and extending display life - a critical requirement for CD74HCT4543EE4 deployments in instrumentation and automotive LCDs.

Can the CD74HCT4543EE4 drive LED displays directly?

Yes, the CD74HCT4543EE4 can drive common-anode LED displays directly using its active-low segment outputs (a–g), provided external current-limiting resistors are used to restrict output sink current to ≤4 mA per segment. It does not support common-cathode LEDs without external inverters or PNP drivers due to its open-drain-like low-side drive architecture.

How does the latch enable (LD) pin affect BCD input sampling in the CD74HCT4543EE4?

In the CD74HCT4543EE4, the LD pin controls latching behavior: when LD is low, the internal latches capture and hold the current D0–D3 BCD inputs; when LD is high, the outputs become transparent to the BCD inputs, updating in real time. This dual-mode operation allows flexible timing - e.g., latching during microcontroller bus contention or enabling dynamic digit updates without flicker.

What is the maximum fanout capability of the CD74HCT4543EE4 over temperature?

The CD74HCT4543EE4 provides a fanout of 10 LSTTL loads over its full operating temperature range (–55°C to +125°C), verified by its guaranteed output drive strength (VOH ≥ 3.7 V at IOH = –4 mA, VOL ≤ 0.4 V at IOL = 4 mA). This ensures reliable interfacing with downstream TTL logic without buffering, even in thermally demanding environments.

Is the CD74HCT4543EE4 RoHS compliant and lead-free?

Yes, the CD74HCT4543EE4 is RoHS compliant and features a NIPDAU (nickel-palladium-gold) lead finish, as confirmed in TI's official packaging addendum. It meets JEDEC J-STD-020 moisture sensitivity requirements and is rated for lead-free reflow soldering, with no MSL restriction due to its PDIP package construction.