STMicroelectronics M74HC245B1R

Overview

M74HC245B1R from STMicroelectronics is an advanced high-speed CMOS octal bus transceiver with 3-state non-inverting outputs, used for bidirectional asynchronous data bus communication. It features directional control (DIR), output enable (G), symmetrical drive (±6mA), 10ns typical propagation delay at 6V, and operates from 2V to 6V. Commonly deployed in microcontroller system data bus isolation and expansion interfaces.

For engineers reviewing the M74HC245B1R datasheet, M74HC245B1R pinout, M74HC245B1R application, or M74HC245B1R equivalent, key selection criteria include 3-state bus isolation timing, VCC range compatibility (2–6V), DIR/G control logic behavior, and DIP-20 package mechanical fit in legacy board designs.

Technical Context

The M74HC245B1R implements a dual-bus bidirectional interface where DIR selects data flow direction (A→B or B→A), while G enables/disables all outputs into high-impedance state. Its C2MOS silicon gate process ensures low static current (4µA max) and high noise immunity (28% VCC min).

Propagation delays are balanced (tPLH ≅ tPHL), output impedance is symmetrical (|IOH| = IOL ≥ 6mA), and input thresholds scale with VCC (VIH = 0.7×VCC min, VIL = 0.3×VCC max), supporting robust operation across the full 2–6V supply range and -55°C to +125°C temperature span.

Key Specifications

Pinout & Package

Package: Plastic DIP-20 (0.300" wide), 2.54mm pitch, through-hole mounting. Dimensions per STMicroelectronics mechanical drawing P001J.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC245N and 74VHC245N, the M74HC245B1R offers superior high-temperature capability (-55°C to +125°C), tighter VOL at 6mA load, and broader 2–6V supply tolerance - making it optimal for industrial and extended-temperature embedded systems where reliability trumps peak speed.

Availability

M74HC245B1R is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and legacy microcontroller bus expansion requiring stable component supply and long-term obsolescence management.

Supply support for M74HC245B1R 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 automotive, industrial, and consumer markets.

The M74HC245B1R belongs to ST's high-speed CMOS logic family, engineered specifically for robust, low-power bidirectional bus interfacing in harsh-temperature and mixed-voltage embedded systems.

FAQ

What is the maximum capacitive load the M74HC245B1R can drive reliably?

The device is characterized up to 150pF load capacitance in AC testing (tPLH/tPHL measured at CL = 50pF and 150pF). Driving >150pF may increase propagation delay beyond spec (e.g., +35ns at 200pF, 6V), so PCB trace capacitance and fanout must be limited to maintain timing integrity in high-speed designs.

Can M74HC245B1R operate with VCC = 3.3V and interface to 5V logic?

Yes - it operates down to 2V and tolerates VI up to VCC + 0.5V. At 3.3V supply, VOH reaches 3.2V (min) at 20µA load, sufficient to drive 74HC/74HCT inputs. However, connecting outputs directly to 5V-tolerant inputs requires external clamping or level-shifting for sustained reliability.

Is the M74HC245B1R pin-compatible with older 74LS245 devices?

Yes - it is functionally and pin-compatible with 74LS245, including identical DIR, G, A/B port assignments and DIP-20 footprint. However, HC logic thresholds differ (VIH = 0.7×VCC vs. LS's 2.0V fixed), so verify input drive strength and noise margins when replacing LS parts in existing designs.

What happens to bus lines during high-impedance (Z) state?

When G = HIGH, all A and B pins enter high-impedance state with leakage ≤ ±5µA (TA ≤ 85°C). Floating bus lines must be externally biased (pull-up/down) to prevent undefined logic states, metastability, or excessive shoot-through current in connected drivers.