Texas Instruments CD74HCT165M-P

Overview

CD74HCT165M-P from Texas Instruments is an 8-bit parallel-in/serial-out shift register with asynchronous parallel load, complementary QH/QH outputs, and TTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2.0 V). It operates at 4.5–5.5 V, supports –55°C to +125°C industrial/military temperature range, and enables daisy-chained parallel-to-serial conversion in microcontroller I/O expansion and data acquisition systems.

For engineers reviewing the CD74HCT165M-P datasheet, CD74HCT165M-P pinout, CD74HCT165M-P application, or CD74HCT165M-P equivalent, key selection criteria include its asynchronous SH/LD control, guaranteed 18 MHz max clock frequency at –55°C to +125°C, complementary serial outputs for noise-immune signal routing, and SOIC-16 package compatibility with legacy 74-series logic layouts.

Technical Context

The CD74HCT165M-P implements a synchronous right-shift architecture triggered on CLK's positive edge when SH/LD is high, while enabling immediate parallel capture of A–H inputs when SH/LD is low - decoupling data loading from clock timing. Its dual-mode operation (parallel load vs. serial shift) is controlled solely by the level of SH/LD, with no internal state machine or enable sequencing required.

CLK INH provides active-high clock inhibition: when high, it blocks all clock transitions from affecting register state, preserving output values regardless of CLK activity. The device delivers complementary QH and QH outputs directly from the final flip-flop stage, supporting differential signal transmission or logic-level inversion without external gates.

Key Specifications

Pinout & Package

CD74HCT165M-P is housed in a 16-pin SOIC (D) package with 9.90 mm × 3.90 mm body size, 1.27 mm lead pitch, and gull-wing leads compatible with standard surface-mount reflow profiles (MSL Level-1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT165N and CD74HC165M96, CD74HCT165M-P uniquely combines TTL-compatible inputs, SOIC-16 surface-mount packaging, and full military-temperature qualification - making it the only option that satisfies all three requirements simultaneously in space-constrained, high-reliability designs.

Availability

CD74HCT165M-P is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive sensor data aggregation, and legacy equipment interface adapter applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT165M-P 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 over 90 years of innovation in high-reliability components for aerospace, industrial, and automotive markets.

The CD74HCT165M-P belongs to TI's 74HCT logic family, engineered specifically for seamless integration with legacy TTL systems while delivering CMOS power efficiency and extended-temperature robustness.

FAQ

What is the maximum clock frequency supported by CD74HCT165M-P across its full temperature range?

The CD74HCT165M-P supports a maximum clock frequency of 18 MHz over the full –55°C to +125°C operating range, as specified in Section 5.5 of the TI datasheet (SCHS156D). This value is measured under worst-case conditions (VCC = 4.5 V, CL = 50 pF), ensuring timing margin for real-world PCB layouts with trace capacitance and noise.

Does CD74HCT165M-P require external pull-up or pull-down resistors on its inputs?

No, CD74HCT165M-P does not require external pull-up or pull-down resistors on any inputs. Its buffered inputs have defined TTL-compatible thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) and input leakage current ≤ ±1 μA, allowing direct connection to microcontroller GPIOs, LSTTL outputs, or open-collector drivers without biasing components.

How does the SH/LD pin function in CD74HCT165M-P, and what happens when it transitions from LOW to HIGH?

The SH/LD pin on CD74HCT165M-P is an active-low asynchronous load control. When LOW, it immediately latches A–H parallel inputs into the register regardless of CLK state. When transitioning from LOW to HIGH, the device enters serial shift mode - subsequent CLK rising edges shift data rightward (A→B→C…→QH), with new bits entering via SER. Per Section 7.3, CLK and CLK INH must be LOW before this transition to prevent unintended shifts.

Can CD74HCT165M-P be used in daisy-chained configurations, and how is this implemented?

Yes, CD74HCT165M-P supports daisy-chaining via its complementary QH and QH outputs. Connect QH of one device to SER of the next to extend the serial chain. Each device loads its 8-bit parallel word asynchronously, then shifts out bits sequentially - enabling N×8-bit parallel-to-serial conversion with a single clock and data line. The functional diagram in Section 4 confirms this topology.

What is the purpose of the CLK INH pin on CD74HCT165M-P, and how does it interact with the main clock?

The CLK INH (Clock Inhibit) pin on CD74HCT165M-P is an active-high signal that overrides CLK functionality: when CLK INH = HIGH, no CLK transitions affect the register state, effectively freezing QH/QH outputs. This allows deterministic pausing of serial shifting without disrupting internal data - critical for interrupt service routines or multi-master bus arbitration. As noted in Section 7.3, CLK INH must be LOW before SH/LD goes HIGH to avoid metastability.