Texas Instruments CD54HCT165F3A

Overview

CD54HCT165F3A from Texas Instruments is a military-grade 8-bit parallel-in/serial-out shift register with complementary QH and Q̅H outputs, asynchronous parallel load (SH/LD), and serial data input (SER). It operates at 4.5 V to 5.5 V, supports -55 °C to +125 °C, delivers 4 mA output drive, and enables daisy-chained parallel-to-serial conversion in rugged embedded control systems.

For engineers reviewing the CD54HCT165F3A datasheet, CD54HCT165F3A pinout, CD54HCT165F3A application, or CD54HCT165F3A equivalent, this page provides verified functional modes, temperature-rated timing specs, complementary output behavior, military-grade packaging details, and real-world interface constraints for high-reliability shift register selection.

Technical Context

The CD54HCT165F3A implements an 8-stage positive-edge-triggered shift register with dual operational modes: asynchronous parallel load when SH/LD is LOW, and serial right-shift (A→B→C→…→H→QH) on each CLK rising edge when SH/LD is HIGH. CLK INH enables clock gating without disrupting register state.

Its HCT logic family ensures direct LSTTL input compatibility (VIL ≤ 0.8 V, VIH ≥ 2.0 V at VCC = 4.5–5.5 V), CMOS-level input leakage (≤1 μA), and guaranteed propagation delays ≤60 ns over full military temperature range (-55 °C to +125 °C) at 4.5 V.

Key Specifications

Pinout & Package

CD54HCT165F3A uses a 16-pin Ceramic Dual In-line Package (CDIP-J) with 24.38 mm × 6.92 mm body size, hermetically sealed for moisture resistance and long-term reliability in extended temperature operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit parallel-in/serial-out shift register applications.

Compared with CD74HCT165E and SN74HCT165N, the CD54HCT165F3A provides mandatory hermetic CDIP packaging, full QML-38535 Class V qualification, and guaranteed parametric performance across -55 °C to +125 °C - making it the only choice for flight-critical or defense system deployments where reliability under extreme thermal stress is non-negotiable.

Availability

CD54HCT165F3A is available at Aetrix Electronics and suitable for industrial PLC expansion, aerospace telemetry interfaces, defense HMI subsystems, and downhole instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD54HCT165F3A 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 ICs with decades of heritage in military-qualified components.

The CD54HCT165F3A belongs to TI's CD54HCT logic family, designed specifically for high-reliability applications demanding extended temperature operation, hermetic packaging, and compliance with MIL-PRF-38535 requirements.

FAQ

What is the maximum clock frequency supported by the CD54HCT165F3A across its full operating temperature range?

The CD54HCT165F3A supports a maximum clock frequency of 18 MHz at -55 °C to +125 °C, as specified in the switching characteristics table under "fMAX" for HCT types. This value reflects worst-case timing across the full military temperature range at VCC = 4.5 V, ensuring reliable operation without setup/hold violations in thermally stressed environments where the CD54HCT165F3A is deployed.

Does the CD54HCT165F3A require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs on the CD54HCT165F3A must be tied to a defined logic level (VCC or GND) per TI layout guidelines. Floating inputs can cause increased ICC, erratic shifting, or latch-up due to undefined internal node voltages. For example, unused SER, CLK INH, or A–H pins should be connected to VCC or GND depending on functional intent; the CD54HCT165F3A datasheet explicitly prohibits leaving any input unconnected.

How does the SH/LD pin interact with CLK and CLK INH during mode transitions?

The CD54HCT165F3A requires CLK and CLK INH to be LOW before SH/LD transitions from HIGH to LOW to prevent unintended shifting. Per the functional truth table and detailed description, violating this sequencing may cause metastability or partial register updates. The CD54HCT165F3A datasheet specifies that CLK INH must remain LOW during SH/LD assertion to ensure clean parallel load behavior - a critical constraint for deterministic control in safety-critical systems using the CD54HCT165F3A.

Can the CD54HCT165F3A be used with 3.3 V logic systems?

No - the CD54HCT165F3A is strictly a 4.5 V to 5.5 V device and is not characterized for 3.3 V operation. Its HCT inputs require VIH ≥ 2.0 V and VIL ≤ 0.8 V referenced to VCC, and its output drive strength degrades outside the specified supply range. Using the CD54HCT165F3A with 3.3 V controllers requires level translation; for native 3.3 V compatibility, consider the CD74HC165 series instead.

What is the purpose of the complementary QH and Q̅H outputs on the CD54HCT165F3A?

The complementary QH (true) and Q̅H (inverted) outputs on the CD54HCT165F3A enable noise-immune signal routing, differential clocking, or direct interfacing with flip-flops requiring both polarities. They allow daisy-chaining without external inverters and support fail-safe designs where one output can serve as redundancy or timing reference. This dual-output capability is intrinsic to the CD54HCT165F3A architecture and is fully characterized across temperature and voltage.