Texas Instruments CD74HC640M

Overview

CD74HC640M from Texas Instruments is an inverting octal three-state bus transceiver in SOIC-20 package, operating from 2 V to 6 V, delivering 15 LSTTL load drive capability, propagation delay as low as 7 ns (at VCC = 4.5 V), and wide temperature range (-55°C to 125°C). It enables bidirectional data flow control between isolated buses in industrial backplane and legacy system upgrades.

For engineers reviewing the CD74HC640M datasheet, CD74HC640M pinout, CD74HC640M application, or CD74HC640M equivalent, key selection criteria include its inverting logic function, DIR/OE dual-control architecture, CMOS-level input compatibility, high-impedance isolation timing, and SOIC-20 thermal performance (RθJA = 58°C/W).

Technical Context

The CD74HC640M implements a silicon-gate CMOS architecture with buffered inputs and three-state outputs, supporting asynchronous bidirectional communication between two 8-bit data buses. Its DIR input selects direction (A→B or B→A), while OE controls output enable/disable with inversion applied to all data paths.

It features balanced propagation delays (tpd ≤ 23 ns over full temperature range at VCC = 4.5 V), low dynamic power dissipation (Cpd = 38 pF), and robust noise immunity (NIL/NIH = 30% of VCC at 5 V), making it suitable for mixed-voltage bus interfacing where signal integrity and bus contention avoidance are critical.

Key Specifications

Pinout & Package

CD74HC640M is housed in a 20-pin SOIC (DW) package measuring 12.80 mm × 7.50 mm with 1.27 mm pitch, 2.65 mm max height, and moisture sensitivity level (MSL) Level-1 (unlimited floor life at <30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC245N and CD74HCT640M, CD74HC640M uniquely combines inverting logic, 2–6 V operation, and DIR/OE dual-control in a drop-in SOIC-20 footprint - essential for space-constrained, mixed-voltage, and polarity-critical bus architectures.

Availability

CD74HC640M is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy system bus extension, military data link interface, and test equipment signal routing requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC640M 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions with over 90 years of innovation in high-reliability IC design.

The CD74HC640M belongs to TI's HC-series high-speed CMOS logic family, engineered for low-power, high-noise-immunity bus interfacing in industrial, aerospace, and automotive control systems where deterministic timing and wide temperature operation are mandatory.

FAQ

What is the logic function of CD74HC640M?

The CD74HC640M is an inverting octal three-state bus transceiver. It transfers data bidirectionally between two 8-bit buses (A and B) with inversion applied to all signals. Direction is controlled by the DIR pin (low = A→B, high = B→A), and output enable is managed by the OE pin (low = active, high = high-impedance). This functionality is explicitly defined in the device functional modes table and confirmed across all electrical and timing specifications in the TI datasheet SCHS192C.

Does CD74HC640M support 3.3 V operation?

Yes, CD74HC640M supports 3.3 V operation as part of its specified 2 V to 6 V supply range. At VCC = 3.3 V, it maintains valid logic thresholds (VIH ≈ 2.31 V, VIL ≈ 0.99 V), delivers typical propagation delay under 15 ns, and sustains 15 LSTTL load drive capability. These parameters are verified in the HC-type electrical characteristics tables and switching characteristics sections of the official TI datasheet.

What is the maximum operating temperature for CD74HC640M?

The CD74HC640M is rated for operation from -55°C to 125°C, as stated in the Recommended Operating Conditions section of the TI datasheet. This extended temperature range is validated across all electrical parameters including propagation delay, output drive, and leakage current, and applies specifically to the SOIC (DW) package variant identified in the orderable addendum.

Is CD74HC640M pin-compatible with CD74HCT640M?

Yes, CD74HC640M and CD74HCT640M share identical SOIC-20 (DW) package dimensions, pin count, pin assignment, and mechanical layout. Both devices use the same 1.27 mm pitch, 12.80 mm × 7.50 mm body size, and pin 1 marking location. This physical and functional pin compatibility is confirmed in TI's PACKAGE OPTION ADDENDUM and Mechanical, Packaging, and Orderable Information sections.

What decoupling capacitor is recommended for CD74HC640M?

A 0.1 µF ceramic capacitor is recommended for CD74HC640M, placed as close as possible to the VCC pin (pin 20) and GND pin (pin 9). TI's Power Supply Recommendations section explicitly states this value and emphasizes minimizing trace inductance for optimal noise suppression. Parallel use of a 1 µF capacitor is acceptable for broader frequency coverage but does not replace the mandatory 0.1 µF local bypass.