Texas Instruments CD74HCT573E

Overview

CD74HCT573E from Texas Instruments is an octal transparent D-type latch with 3-state outputs, designed for bus-oriented bidirectional data latching in TTL-compatible digital systems. It operates from 4.5 V to 5.5 V, supports −55°C to 125°C temperature range, features balanced propagation delays (35–53 ns), drives up to 10 LS-TTL loads, and provides high-impedance output control via OE for shared-bus applications.

For engineers reviewing the CD74HCT573E datasheet, CD74HCT573E pinout, CD74HCT573E application, or CD74HCT573E equivalent, key selection criteria include latch-enable timing (tsu = 13–20 ns, th = 10–15 ns), 3-state output drive capability, PDIP-20 package compatibility with through-hole prototyping, and industrial-grade thermal performance (RθJA = 84.6°C/W).

Technical Context

The CD74HCT573E implements eight independent D-type transparent latches controlled by a shared latch-enable (LE) input: when LE is high, Q outputs mirror D inputs; when LE goes low, outputs retain the last D value. A separate buffered output-enable (OE) input places all eight outputs simultaneously into high-impedance state without affecting internal latch operation.

This dual-control architecture enables asynchronous data capture and synchronous bus release - critical for microprocessor address/data bus isolation, memory interfacing, and I/O port expansion where data must be held stable while outputs are tri-stated for bus sharing.

Key Specifications

Pinout & Package

CD74HCT573E is housed in a 20-pin Plastic Dual In-line Package (PDIP-N) with 0.300-inch body width and 0.100-inch lead pitch, optimized for through-hole mounting and manual prototyping.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal transparent latch applications.

Compared with SN74HCT573N, CD74HCT573E offers identical functionality in the same PDIP package but may differ in traceability or qualification history; versus 74HCT573D, it trades SMT scalability for mechanical robustness and hand-soldering accessibility in development and field service contexts.

Availability

CD74HCT573E is available at Aetrix Electronics and suitable for industrial control systems, legacy equipment repair, and educational electronics labs requiring stable component supply with long-lifecycle support.

Supply support for CD74HCT573E 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 decades of expertise in high-reliability logic families.

The CD74HCT573E belongs to TI's HCT (High-Speed CMOS TTL-compatible) logic series, engineered for drop-in replacement of LS-TTL in industrial and automotive applications demanding low power, wide temperature range, and robust noise immunity.

FAQ

What is the maximum clock or data frequency supported by CD74HCT573E?

The CD74HCT573E does not operate on a clock signal - it is a transparent latch controlled by level-sensitive LE. Its usable data rate depends on timing parameters: minimum LE pulse width is 16–24 ns, and data must be stable 13–20 ns before LE falls. For repetitive latching, maximum effective rate is ~10–15 MHz under typical conditions. The CD74HCT573E is not rated for continuous high-frequency toggling like a flip-flop.

Can CD74HCT573E drive LED indicators directly without current-limiting resistors?

No. While CD74HCT573E can sink or source up to 6 mA per output, driving LEDs directly risks exceeding absolute maximum ratings and damaging the outputs. Each Q output requires a series current-limiting resistor calculated for desired LED brightness and VCC (e.g., 330 Ω for ~10 mA at 5 V). The CD74HCT573E is intended for logic-level interfacing, not power driving.

Is CD74HCT573E compatible with 3.3-V microcontrollers?

CD74HCT573E inputs are TTL-compatible (VIH = 2.0 V min), so 3.3-V logic HIGH levels meet this requirement. However, its outputs swing to 5 V (VOH ≈ 3.98 V at 6 mA), which may exceed 3.3-V input tolerances. Use level-shifting circuitry or verify receiver input voltage limits before connecting CD74HCT573E outputs to 3.3-V devices. The CD74HCT573E itself must be powered at 4.5–5.5 V.

How should unused inputs be handled on CD74HCT573E?

All unused D inputs and control inputs (LE, OE) on CD74HCT573E must be tied to a valid logic level - either VCC or GND - to prevent floating nodes that cause excessive current draw, oscillation, or undefined output states. TI recommends tying unused D inputs to GND and unused LE/OE to VCC (via pull-up for OE to ensure Hi-Z at power-up). Leaving any input unconnected violates recommended operating conditions for the CD74HCT573E.

Does CD74HCT573E support hot insertion or live bus connection?

No. CD74HCT573E is not designed for hot-plug operation. Its absolute maximum ratings specify VI and VO limits relative to VCC/GND, and applying voltage to inputs or outputs before VCC is stable may activate parasitic paths and cause latch-up or permanent damage. Always power VCC before applying signals. For hot-swap applications, consider dedicated hot-swap controllers or buffers with power sequencing support instead of relying on CD74HCT573E.