Texas Instruments CD74HCT4543EG4

Overview

CD74HCT4543EG4 from Texas Instruments is a high-speed CMOS BCD-to-7-segment latch/decoder/driver IC designed for direct LCD segment driving. It operates from 4.5 V to 5.5 V, features active-high latch enable (LD), blanking input (BI), and phase input (PH) for AC-coupled LCD bias, and delivers balanced propagation delays (≤120 ns at 4.5 V) with TTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2 V).

For engineers reviewing the CD74HCT4543EG4 datasheet, CD74HCT4543EG4 pinout, CD74HCT4543EG4 application, or CD74HCT4543EG4 equivalent, key selection considerations include its dedicated LCD drive capability with PH-controlled output complementation, latch transparency mode, and compatibility with legacy LSTTL logic levels in industrial display subsystems.

Technical Context

The CD74HCT4543EG4 integrates three functional blocks: input latches synchronized to LD, a BCD-to-7-segment decoder with active-low outputs, and segment drivers capable of sinking up to 4 mA per output. Its PH input toggles all segment outputs in-phase or out-of-phase relative to the LCD backplane square wave - essential for preventing DC bias in liquid-crystal cells.

Latch operation is edge-triggered on LD falling edge: when LD is low, BCD inputs (D0–D3) are stored; when LD is high, outputs follow inputs transparently. BI forces all outputs low (blanking), independent of LD state. The device uses silicon-gate HCT technology, delivering CMOS power efficiency (<160 µA ICC max) with LSTTL-level input thresholds and fanout of 10 LSTTL loads.

Key Specifications

Pinout & Package

CD74HCT4543EG4 is housed 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 (2.54 mm), compatible with standard PCB layouts and socketing.

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 CD74HCT4543EG4 uniquely combines TTL-compatible inputs, integrated LCD-specific PH control, and low-power HCT logic - making it the optimal choice for 5 V microcontroller-driven LCD displays requiring minimal external components and guaranteed AC bias compliance.

Availability

CD74HCT4543EG4 is available at Aetrix Electronics and suitable for industrial panel meters, automotive instrument clusters, test equipment, and appliance control panels requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT4543EG4 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, automotive, and consumer reach.

The CD74HCT4543EG4 belongs to TI's legacy HCT logic family, engineered specifically for robust, low-power BCD-driven display interfaces in harsh-environment applications where reliability, temperature resilience, and direct LCD compatibility are mandatory.

FAQ

What is the primary function of the PH pin on the CD74HCT4543EG4?

The PH (Phase) pin on the CD74HCT4543EG4 accepts a square-wave signal (GND to VCC) that synchronously complements all seven segment outputs (a–g). This ensures AC coupling to the LCD backplane, eliminating DC voltage buildup that causes electrochemical degradation in liquid-crystal cells - a critical requirement for long-term LCD reliability. The PH input directly controls output polarity without affecting latch or decode logic.

Does the CD74HCT4543EG4 support common-anode or common-cathode LCD configurations?

The CD74HCT4543EG4 provides active-low segment outputs (a–g), making it inherently compatible with common-anode LCDs where each segment connects between VCC and the driver output. For common-cathode LCDs, external inverters or redesign would be required - the device is optimized for common-anode AC-driven displays per its PH and BI architecture and application circuits in the datasheet.

Can the CD74HCT4543EG4 drive LEDs directly, or is it limited to LCDs?

The CD74HCT4543EG4 is rated for 4 mA sink per output (VOL = 0.4 V @ 4 mA), which is insufficient for standard LEDs requiring 10–20 mA. Its output structure, PH synchronization, and blanking behavior are explicitly designed for LCD bias control - not LED current drive. Driving LEDs would require external transistor buffers or dedicated LED drivers like the TLC5916.

What happens to the outputs when LD is high and BI is asserted on the CD74HCT4543EG4?

When LD is high (transparent mode) and BI is high (blanking enabled), all segment outputs (a–g) are forced low immediately - overriding both the live BCD inputs and any previously latched value. This behavior is unconditional and occurs regardless of PH state or input transitions, enabling rapid display blanking during system initialization, fault conditions, or multiplexing intervals.

Is the CD74HCT4543EG4 pin-compatible with the CD74HCT4543E or CD74HCT4543EE4?

Yes - CD74HCT4543EG4, CD74HCT4543E, and CD74HCT4543EE4 share identical PDIP-16 packaging, pinout, electrical specifications, and functional behavior. The "G4" and "EE4" suffixes denote TI's RoHS-compliant lead finish (NiPdAu/NiPdAu), while "E" indicates standard NiPdAu; all three are functionally and mechanically interchangeable in existing designs.