STMicroelectronics M74HC165B1R

Overview

M74HC165B1R from STMicroelectronics is a high-speed CMOS 8-bit parallel-in/serial-out (PISO) shift register with asynchronous parallel load, operating from 2V to 6V supply, featuring 15ns typical propagation delay at 6V, ±4mA output drive, and pin/function compatibility with standard 74-series 165 devices. It is used in microcontroller GPIO expansion, industrial I/O consolidation, and serial data acquisition systems.

For engineers reviewing the M74HC165B1R datasheet, M74HC165B1R pinout, M74HC165B1R application, or M74HC165B1R equivalent, key selection criteria include its dual-clock input architecture with clock inhibit capability, symmetrical output impedance, wide VCC range, and guaranteed operation across –55°C to +125°C.

Technical Context

The M74HC165B1R implements an 8-bit master-slave RS flip-flop shift register with over-riding asynchronous parallel load control via the SHIFT/LOAD input. Its two clock inputs (CLOCK and CLOCK INH) feed a 2-input NOR gate, enabling dynamic clock gating without double-clocking when CLOCK INH transitions only during HIGH clock state.

Input protection includes ESD and transient voltage suppression circuits. Propagation delays are balanced (tPLH ≅ tPHL), and noise immunity is specified at ≥28% VCC for both VIH and VIL thresholds, supporting robust operation in electrically noisy industrial environments.

Key Specifications

Pinout & Package

Package: Plastic DIP-16 (0.300" width), JEDEC MS-001, body dimensions 20.0 × 8.5 mm, lead pitch 2.54 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PISO shift register applications.

Compared with SN74HC165N and 74LV165A, the M74HC165B1R offers superior temperature resilience, lowest quiescent current, and integrated clock inhibit - making it optimal for industrial and automotive applications demanding reliability, low power, and deterministic timing control.

Availability

M74HC165B1R is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive body control modules, and test equipment digital pattern capture requiring stable component supply and long-term lifecycle support.

Supply support for M74HC165B1R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The M74HC165B1R belongs to ST's high-reliability HC logic family, engineered for robust operation in harsh environments with extended temperature range, ESD-hardened inputs, and consistent timing behavior across voltage and temperature.

FAQ

What is the function of the CLOCK INH pin on the M74HC165B1R?

The CLOCK INH (Clock Inhibit) pin is an active-HIGH input that disables the internal clock path via a 2-input NOR gate shared with the CLOCK pin. When HIGH, it prevents clock edge detection regardless of CLOCK signal state. To avoid unintended triggering, CLOCK INH must transition only while CLOCK is HIGH - otherwise a rising CLOCK INH edge mimics a clock edge and causes spurious shift.

Can the M74HC165B1R operate reliably at 2.0V supply?

Yes - the M74HC165B1R is fully specified down to 2.0V, with guaranteed VIH ≥1.5V and VIL ≤0.5V, tPD ≤225ns (max), and fMAX ≥7.4MHz. Its C2MOS silicon gate technology ensures stable switching and noise immunity even at minimum VCC, making it suitable for battery-powered or low-voltage embedded systems.

How does the M74HC165B1R handle simultaneous parallel load and serial shift operations?

The device uses priority logic: when SHIFT/LOAD is LOW, parallel data A–H is loaded asynchronously into the register regardless of clock activity. When SHIFT/LOAD goes HIGH, the device enters serial shift mode on subsequent CLOCK edges. The transition from parallel load to shift is atomic - no intermediate or metastable state occurs if setup/hold times are met.

Is the M74HC165B1R pin-compatible with older 74LS165 devices?

Yes - the M74HC165B1R is pin- and function-compatible with the 74LS165, including identical pin numbering, logic behavior, and truth table. However, it operates at higher speed, lower power, and wider voltage range. Level-shifting is not required when replacing LS parts in 5V systems, but note that HC outputs drive heavier loads than LS and may require series termination in long-trace applications.