STMicroelectronics M74HCT640RM13TR

Overview

M74HCT640RM13TR from STMicroelectronics is an octal bus transceiver with 3-state inverted outputs, designed for bidirectional asynchronous data bus interfacing. It features 13 ns typical propagation delay at 4.5 V, ±6 mA symmetrical output drive, TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V), and operates across –55 °C to +125 °C. Used in industrial backplane isolation and legacy system bus bridging where direction control and high-impedance decoupling are required.

For engineers reviewing the M74HCT640RM13TR datasheet, M74HCT640RM13TR pinout, M74HCT640RM13TR application, or M74HCT640RM13TR equivalent, key selection criteria include DIR-controlled bidirectional flow, G-gated 3-state enable/disable timing (tPZL/tPLZ ≤ 45 ns), rail-to-rail CMOS output compatibility with TTL inputs, and TSSOP20 packaging for space-constrained PCB layouts.

Technical Context

The M74HCT640 implements dual 8-bit data paths with independent directional control via DIR and global 3-state enable via G. Its C2MOS silicon gate process ensures low static current (ICC ≤ 4 µA) while maintaining TTL-level input compatibility and symmetrical IOH/IOL drive strength.

Propagation delays are balanced (tPLH ≅ tPHL), and all inputs include ESD protection. The device requires external biasing of floating bus lines during high-impedance states, and its logic diagram confirms inversion on both A→B and B→A paths per truth table behavior.

Key Specifications

Pinout & Package

TSSOP20 package: 6.5 mm × 4.4 mm body, 0.65 mm pitch, 1.2 mm height, lead-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver applications.

Compared with SN74HCT640N and 74VHC640M, the M74HCT640RM13TR offers optimal balance of industrial temperature range, TSSOP20 space efficiency, and proven 5 V bus drive margin - making it preferred for volume SMT deployment in ruggedized embedded systems.

Availability

M74HCT640RM13TR is available at Aetrix Electronics and suitable for industrial backplane isolation, legacy system bus bridging, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for M74HCT640RM13TR 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, designing and manufacturing analog, digital, and mixed-signal ICs for industrial, automotive, and consumer applications.

The M74HCT640 belongs to ST's high-speed CMOS logic family, engineered specifically for robust 5 V bus interfacing in mission-critical industrial and automotive control systems.

FAQ

Is M74HCT640RM13TR compatible with 3.3 V logic systems?

No. The M74HCT640RM13TR is specified only for 4.5–5.5 V operation and lacks 3.3 V input tolerance. Its VIH minimum is 2.0 V, but DC output levels (VOH ≥ 4.1 V at 6 mA) exceed 3.3 V rail limits, risking damage to downstream 3.3 V receivers. Use level-shifting circuitry or a 3.3 V–compatible transceiver such as 74LVC640 for mixed-voltage designs.

What is the maximum capacitive load this device can drive reliably?

The M74HCT640RM13TR is characterized up to 150 pF (see AC specs: tPLH/tPHL tested at CL = 50 pF and 150 pF). Driving >150 pF risks exceeding 33 ns max propagation delay and may cause signal integrity issues like ringing or setup/hold violations. For heavier loads, add series termination or reduce trace length; do not exceed 150 pF without empirical validation.

How should unused inputs be handled?

All unused inputs - including DIR and G - must be tied to a valid logic level (VCC or GND) to prevent floating states that cause excessive ICC, oscillation, or ESD susceptibility. Floating DIR or G pins may induce unintended direction changes or partial enablement, leading to bus contention. Do not leave any input unconnected, even during test or debug phases.

Does this part support hot insertion or live bus swapping?

No. The M74HCT640RM13TR lacks hot-swap protection circuitry such as slew-rate limiting or power-up sequencing control. Inserting or removing the device while VCC or bus signals are active may cause latch-up, ground bounce, or transient overstress on connected drivers. Always power down the system before module replacement or board rework.