STMicroelectronics 74AC74TTR

Overview

74AC74TTR from STMicroelectronics is a dual D-type flip-flop with asynchronous preset and clear, designed for high-speed synchronous logic in 5V and mixed-voltage systems. It operates from 2V to 6V, delivers 300MHz typical maximum clock frequency at VCC = 5V, features symmetrical 24mA output drive, and supports 50Ω transmission line driving - used in clock distribution, state machines, and data latching in industrial control and communications interfaces.

For engineers reviewing the 74AC74TTR datasheet, 74AC74TTR pinout, 74AC74TTR application, or 74AC74TTR equivalent, key selection criteria include propagation delay matching (tPLH ≅ tPHL), asynchronous set/clear timing margins, 50Ω line-driving capability, ESD immunity (2kV), and TSSOP-14 package compatibility with high-density PCB layouts.

Technical Context

This device implements two independent edge-triggered D flip-flops with active-low asynchronous reset (CLR) and preset (PR) inputs, triggered on the LOW-to-HIGH clock transition. Each flip-flop transfers the D-input state to Q and Q̅ outputs synchronously, while PR/CLR override clock action with guaranteed minimum pulse widths of 4.0ns (VCC = 5V).

It uses sub-micron C2MOS technology enabling low ICC (2µA max at 25°C), high noise immunity (VNIH/VNIL ≥ 28% VCC), and balanced AC performance: tPLH/tPHL ≤ 12.0ns (VCC = 5V, CL = 50pF), setup/hold times of 3.0ns/2.0ns, and fMAX up to 300MHz (typical).

Key Specifications

Pinout & Package

TSSOP-14 package: 4.9mm × 6.4mm body, 0.65mm pitch, 1.1mm height, lead-free, RoHS-compliant surface-mount outline optimized for automated assembly and thermal dissipation in dense logic arrays.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual D-type flip-flop applications.

Compared with SN74AC74PWR and MC74AC74DT, the 74AC74TTR offers the lowest quiescent current (40µA max over full temp range) and highest typical clock frequency (300MHz), making it optimal for high-speed, low-power industrial timing and synchronization where thermal headroom is constrained.

Availability

74AC74TTR is available at Aetrix Electronics and suitable for industrial PLC timing modules, serial data synchronizers, digital audio clock dividers, and test equipment pattern generators requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74AC74TTR 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, specializing in microcontrollers, power management, analog ICs, and discrete devices for industrial, automotive, and consumer markets.

The 74AC logic family targets high-speed, low-power TTL-compatible digital interfacing and sequencing, with emphasis on robustness in harsh environments and seamless integration into mixed-voltage systems.

FAQ

What is the minimum clock pulse width required for reliable operation of 74AC74TTR?

The minimum HIGH and LOW clock pulse width is 4.0ns at VCC = 5V across the full operating temperature range (-55°C to +125°C). This specification ensures proper triggering of the internal edge-detection circuitry and prevents metastability or skipped transitions during high-frequency operation.

Can 74AC74TTR operate reliably at 3.3V supply voltage?

Yes - 74AC74TTR is fully specified from 2V to 6V, including 3.3V operation. At VCC = 3.3V, it guarantees fMAX ≥ 90MHz, tPLH/tPHL ≤ 16.0ns, and VIH/VIL thresholds scaled to 2.1V/1.5V, making it compatible with standard 3.3V CMOS logic families without level-shifting.

Does 74AC74TTR support hot-swap or live-insertion?

No - the device lacks Ioff protection or power-off isolation. Applying input signals while VCC is unpowered may cause latch-up or excessive current through input diodes. Power sequencing must ensure VCC is stable before applying any input signals, per absolute maximum ratings (VI limited to -0.5V to VCC + 0.5V).

How does the 74AC74TTR handle simultaneous assertion of PRESET and CLEAR?

When both PR and CLR are asserted LOW simultaneously, the outputs enter an undefined state (Q and Q̅ may both go HIGH briefly), then settle unpredictably upon release. The datasheet explicitly prohibits this condition; design must ensure mutual exclusion via external gating or priority encoding to avoid metastable behavior.