STMicroelectronics 74LCX245TTR

Overview

74LCX245TTR from STMicroelectronics is a low-voltage CMOS octal bus transceiver (3-state) with 5V-tolerant inputs/outputs, operating from 2.0V to 3.6V, delivering 7.0 ns max propagation delay at VCC = 3V, ±24 mA output drive, and pin/function compatibility with standard 74-series 245 devices for bidirectional data bus isolation in 3.3V systems interfacing to 5V logic.

For engineers reviewing the 74LCX245TTR datasheet, 74LCX245TTR pinout, 74LCX245TTR application, or 74LCX245TTR equivalent, key selection criteria include 5V tolerance on all I/Os, symmetrical 24 mA drive capability, power-down protection, balanced tPLH/tPHL delays, and TSSOP-20 package suitability for space-constrained board designs.

Technical Context

This transceiver implements asynchronous bidirectional data flow between two 8-bit buses using DIR to control direction and G to enable/disable outputs into high-impedance state. All I/Os feature built-in ESD protection (>2 kV HBM) and tolerate 0–5.5 V input voltages regardless of VCC level.

It operates within a 2.0–3.6 V supply range while maintaining full 5V signal interoperability-enabling safe connection to legacy 5V peripherals without level shifters. Propagation delays are tightly matched (tPLH ≅ tPHL), and output skew is limited to 1.0 ns across all channels at 3.0–3.6 V.

Key Specifications

Pinout & Package

TSSOP-20 package: 6.5 mm × 4.4 mm body, 0.65 mm pitch, 1.05 mm max height, lead-free and RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74LCX245TTR, the 74LVC245APW lacks native 5V tolerance and offers reduced drive below 3.0 V, while SN74LVCH245AQPWRQ1 adds automotive qualification and higher ESD rating at the cost of slightly higher quiescent current and price.

Availability

74LCX245TTR is available at Aetrix Electronics and suitable for industrial PLC backplanes, low-power FPGA I/O expansion, PCI bus signal conditioning, and automotive body control module bus bridges requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74LCX245TTR 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 markets.

The 74LCX logic family targets low-voltage, high-speed 3.3V systems requiring 5V signal interoperability-optimized for power-sensitive, space-constrained embedded interfaces where pin compatibility with legacy 74-series logic is essential.

FAQ

Can 74LCX245TTR operate with VCC = 2.5V while interfacing to 5V inputs?

Yes. The device is fully specified for VCC = 2.0–3.6 V and guarantees 5V-tolerant inputs across that entire range. At VCC = 2.5 V, VIH remains 2.0 V and VIL stays at 0.8 V, ensuring reliable detection of 5V logic levels without damage or functional degradation.

What happens to outputs when VCC = 0V and 5V signals are applied to inputs?

Power-down protection prevents reverse current flow: inputs clamp safely, and outputs remain in high-impedance state with <10 µA off-leakage (Ioff). This avoids back-driving powered-down sections of the system and complies with JEDEC JESD78 latch-up immunity requirements.

Is DIR pin level-sensitive or edge-triggered?

The DIR pin is level-sensitive and asynchronous. Data direction changes immediately upon DIR transition (LOW → HIGH or HIGH → LOW), with no clock or setup requirement. Propagation delay from DIR to output reflects the same tPLH/tPHL spec (≤7.0 ns), enabling real-time bus arbitration.

Does 74LCX245TTR require pull-up or pull-down resistors on floating bus lines?

Yes. During high-impedance (3-state) operation, all unused A or B bus lines must be externally held HIGH or LOW-floating nodes may cause undefined logic states, increased ground bounce, or excessive ICC due to internal input stage ambiguity. Typical values are 10 kΩ to VCC or GND.