Texas Instruments CD74HCT4543E

Overview

CD74HCT4543E from Texas Instruments is a BCD-to-7-segment latch/decoder/driver IC designed for direct driving of liquid-crystal displays (LCDs). It features input latching, active-high blanking (BI), phase inversion control (PH), 4.5–5.5 V operation, and LSTTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2 V). Its balanced propagation delay (≤120 ns) and low quiescent current (8 µA typical) support reliable multiplexed LCD interface in industrial panel meters.

For engineers reviewing the CD74HCT4543E datasheet, CD74HCT4543E pinout, CD74HCT4543E application, or CD74HCT4543E equivalent, key selection criteria include its dedicated PH input for AC-coupled LCD backplane drive, latch enable (LD) transparency mode, blanking-controlled display suppression, and compatibility with both CMOS and LSTTL logic families.

Technical Context

The CD74HCT4543E integrates three functional blocks: a 4-bit transparent latch (enabled when LD = LOW), a BCD-to-7-segment decoder, and segment drivers capable of sourcing/sinking up to 4 mA per output. Its PH input toggles output polarity to match AC-driven LCD requirements, while BI forces all segment outputs LOW for blanking.

Latch timing is defined by setup (12 ns min) and hold (8 ns min) times relative to LD↓, and propagation delays range from 32 ns (CL = 15 pF) to 120 ns (CL = 50 pF). Input loading is specified in unit loads (LD = 1.5, PH = 1.25), and fanout supports 10 LSTTL loads over temperature.

Key Specifications

Pinout & Package

CD74HCT4543E is housed in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and 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/driver applications.

Compared with SN74LS47N and CD4543BE, the CD74HCT4543E uniquely combines latch storage, PH-controlled LCD polarity inversion, and true TTL-compatible inputs in a single 5 V device - making it the only option supporting AC-driven LCDs without external logic or level translation.

Availability

CD74HCT4543E is available at Aetrix Electronics and suitable for industrial panel meters, automotive instrument clusters, and test equipment displays requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT4543E 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial and automotive qualification.

The CD74HCT4543E belongs to TI's High-Speed CMOS (HCT) logic family, engineered to replace LSTTL with lower power and identical input thresholds while maintaining pin-for-pin compatibility with legacy 74-series functions.

FAQ

What is the primary function of the PH pin on the CD74HCT4543E?

The PH (Phase) pin on the CD74HCT4543E accepts an external square wave used to invert segment output polarity synchronously with the LCD backplane signal. This AC-coupling method prevents electrolytic degradation in liquid-crystal displays. The CD74HCT4543E uses this pin to generate complementary segment drive signals without external circuitry - a feature absent in standard 7-segment decoders like the SN74LS47N.

Can the CD74HCT4543E drive common-anode LED displays directly?

No, the CD74HCT4543E provides active-HIGH segment outputs optimized for common-cathode LCDs and low-current LEDs. Driving a common-anode LED display would require external inverters or NPN transistor buffers. In contrast, devices like the SN74LS47N offer open-collector outputs specifically designed for common-anode LEDs with built-in current limiting.

What happens to segment outputs when the BI pin is asserted HIGH on the CD74HCT4543E?

When the BI (Blanking Input) pin is driven HIGH, all seven segment outputs (a–g) of the CD74HCT4543E are forced LOW regardless of BCD input or latch state. This hardware-blanking function suppresses display output instantly - useful during system initialization, error states, or multiplexed digit scanning. The CD74HCT4543E does not enter a high-impedance state; outputs remain actively driven LOW.

Is the CD74HCT4543E compatible with 3.3 V microcontrollers?

The CD74HCT4543E requires a 4.5–5.5 V VCC supply and is not 3.3 V tolerant. Its VIH minimum is 2.0 V, but input structure is designed for 5 V logic levels. Direct connection to 3.3 V GPIO may cause unreliable switching or excessive input current. For 3.3 V systems, level-shifting or selecting a 3.3 V–compatible alternative like the SN74LVC4543 is recommended instead of using the CD74HCT4543E.

How does the latch enable (LD) pin affect data flow in the CD74HCT4543E?

When LD is LOW, the CD74HCT4543E latches and holds the current BCD input (D0–D3), decodes it, and drives corresponding segments - isolating display output from input changes. When LD is HIGH, the CD74HCT4543E operates transparently: segment outputs update immediately with BCD input transitions. This dual-mode operation allows precise timing control in systems where display updates must be synchronized to external events or ADC conversions.