STMicroelectronics 74ACT299TTR

Overview

74ACT299TTR from STMicroelectronics is an advanced high-speed CMOS 8-bit parallel-in/parallel-out (PIPO) shift register with asynchronous clear, 3-state outputs, and TTL-compatible input thresholds. It operates from 4.5V to 5.5V, delivers symmetrical 24mA drive capability, supports 240MHz max clock frequency (typ.), and implements four functional modes (HOLD, SHIFT LEFT, SHIFT RIGHT, LOAD) via S0/S1 select inputs. It is used in bus interface logic, data serialization/deserialization, and digital control state management in industrial PLC I/O modules.

For engineers reviewing the 74ACT299TTR datasheet, 74ACT299TTR pinout, 74ACT299TTR application, or 74ACT299TTR equivalent, key selection criteria include its 20-pin TSSOP package, asynchronous active-low CLEAR, dual serial shift directions (SL/SR), 3-state enable control (G1/G2), and guaranteed 50Ω transmission line driving performance at 5V.

Technical Context

The 74ACT299TTR integrates a synchronous edge-triggered 8-bit register with independent serial left/right inputs and parallel I/O terminals (A–H/QA–QH) that function bidirectionally under mode control. Its asynchronous CLEAR resets all flip-flops independently of clock timing, while G1/G2 jointly enable high-impedance output states without halting internal register operation.

It uses sub-micron C2MOS technology for low ICC (8µA max at 25°C) and high noise immunity (2kV ESD), with balanced tPLH/tPHL propagation delays (≤11.4ns at 5V) and guaranteed 50Ω line driving into terminated loads. Input thresholds (VIH ≥2.0V, VIL ≤0.8V) ensure direct interfacing with TTL, NMOS, and CMOS logic families.

Key Specifications

Pinout & Package

74ACT299TTR is housed in a 20-lead TSSOP (Thin Shrink Small Outline Package) with 0.65mm lead pitch, JEDEC MO-153 compliant, body dimensions 6.5 × 6.4 × 1.1mm (D × E × A2).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit PIPO shift register applications.

Compared with SN74ACT299N and MC74ACT299DT, the 74ACT299TTR offers superior board density, lower junction-to-ambient thermal resistance, and RoHS-compliant packaging-making it optimal for volume production of compact, thermally managed industrial electronics.

Availability

74ACT299TTR is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive body control modules, and digital test equipment data capture requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for 74ACT299TTR 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 industrial, automotive, and consumer markets.

The 74ACT299TTR belongs to ST's Advanced CMOS Logic (ACT) product line, engineered for high-speed, low-power, TTL-compatible interface bridging in noise-immune industrial control and instrumentation systems.

FAQ

What is the minimum pulse width required on the CLEAR input?

The minimum active-low CLEAR pulse width is 5.0ns at VCC = 5.0V, as specified in the AC Electrical Characteristics table. This ensures reliable asynchronous reset across the full operating temperature range (–55°C to +125°C) and guarantees metastability-free clearing of all eight internal flip-flops without dependence on clock timing or mode state.

Can G1 and G2 be tied together and driven by a single controller signal?

Yes - G1 and G2 are logically OR'd internally, so tying them together and driving with one active-low signal achieves identical 3-state control behavior. This simplifies GPIO usage and reduces routing complexity, provided the combined load remains within the driver's fan-out capability (verified at ≤24mA sink per pin).

Does the 74ACT299TTR support hot insertion into a live bus?

No - while the device features 2kV ESD protection and high-impedance outputs when G1/G2 are HIGH, it lacks powered-off protection circuitry (e.g., Ioff). Inserting or removing the device while VCC is applied risks bus contention, latch-up, or transient overvoltage on shared lines unless strict power sequencing and bus isolation are implemented externally.

How does the QA′–QH′ output differ from QA–QH in operation?

QA′–QH′ are standard CMOS outputs (not 3-state) that mirror the internal register contents continuously, regardless of G1/G2 state. In contrast, QA–QH are bidirectional I/O pins that become high-impedance when G1/G2 are HIGH and only drive valid logic levels during LOAD, HOLD, or SHIFT modes - making QA′–QH′ ideal for monitoring, while QA–QH serve bus interface functions.