Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

Home > Products > Integrated Circuits (ICs) > Logic > Buffers, Drivers, Receivers, Transceivers

Texas Instruments CD74AC646M

Name: CD74AC646M
Brand: Texas Instruments
SKU: CD74AC646M
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: CD74AC646M

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 24-SOIC (0.295", 7.50mm Width)

Datasheet:: CD74AC646M.pdf

Description:: IC TXRX NON-INVERT 5.5V 24SOIC

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:265

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

CD74AC646M from Texas Instruments is a 16-bit bus transceiver with 3-state outputs and dual-function octal latch/line driver architecture, operating at V_CC = 3.3 V to 5.5 V, featuring t_PD = 9.5 ns typical propagation delay and ±24 mA output drive capability, used in bidirectional data bus isolation for industrial control backplanes.

For engineers reviewing the CD74AC646M datasheet, CD74AC646M pinout, CD74AC646M application, or CD74AC646M equivalent, key selection factors include its TTL-compatible input thresholds, symmetric high/low output drive strength, wide temperature range (–55°C to +125°C), and SOIC-24 package compatibility with legacy 74AC logic systems.

Technical Context

The CD74AC646M implements two independent 8-bit bidirectional transceivers, each with separate Output Enable (OE) and Direction (DIR) controls, enabling full-duplex or half-duplex bus communication. It uses advanced CMOS silicon-gate technology for low static power consumption (I_CC = 8 µA max at 25°C) and noise immunity.

Its input structure includes Schmitt-trigger action on control pins (OE, DIR) for improved noise rejection in noisy industrial environments, and all I/Os are rated for 5.5 V absolute maximum voltage regardless of V_CC, supporting mixed-voltage interface translation between 3.3 V and 5 V domains.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	3.3 V to 5.5 V - supports direct interfacing with both 3.3 V and 5 V logic families without level shifters
t_PD (max)	12.5 ns at V_CC = 5 V - enables reliable operation in 40 MHz bus cycles with timing margin
I_OH/I_OL	–24 mA / +24 mA - drives standard TTL loads and long PCB traces without external buffers
Operating Temp	–55°C to +125°C - qualified for extended-temperature industrial and aerospace applications
I_CC (max)	8 µA at 25°C - reduces system standby power in battery-backed or energy-sensitive designs
Input Threshold	V_IH = 2.0 V min, V_IL = 0.8 V max - ensures robust recognition of TTL-level signals across full V_CC range

Pinout & Package

CD74AC646M is housed in a 24-pin SOIC (DW) package with 300-mil body width, gull-wing leads, and JEDEC MS-013 compliant footprint. Pin 1 is located at the top-left corner with notch orientation marking.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 3, 4, 5, 6, 7, 8	Port A I/O	Bidirectional data lines for first 8-bit bus segment; 3-state when OE_A = high
9, 10, 11, 12, 13, 14, 15, 16	Port B I/O	Bidirectional data lines for second 8-bit bus segment; 3-state when OE_B = high
17, 18	DIR_A, DIR_B	Direction control inputs - high enables A→B flow, low enables B→A flow per port
19, 20	OE_A, OE_B	Output enable inputs - low enables transceiver function, high forces 3-state on respective port
21, 22, 23, 24	GND, V_CC, NC, NC	Ground, supply, and two no-connect pins - V_CC powers both transceivers; NC pins are unused die pads

Key Features

Feature	Design Value
Dual 8-bit bidirectional transceivers	Enables independent control of two data paths - eliminates need for discrete direction logic in multi-bus systems
3-state outputs with separate OE/DIR	Allows dynamic bus arbitration and hot-swap-safe isolation without glitching during state transitions
TTL-compatible input thresholds	Ensures interoperability with legacy 74LS/74ALS systems without pull-up resistors or voltage translators
5.5 V tolerant I/Os	Permits safe connection to higher-voltage buses while powered from 3.3 V - prevents latch-up in mixed-supply systems
Extended temperature range	Validated operation from –55°C to +125°C - suitable for under-hood automotive ECUs and outdoor telecom equipment

Applications

Industrial Backplane Interface	Test Equipment Data Bus
Use Scenario: Isolating CPU and peripheral modules on a modular PLC rack with shared 16-bit address/data bus. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow direction and enabling/disabling per slot under microcontroller control. Use Value: Prevents bus contention during hot-insertion of modules and supports deterministic timing with sub-13 ns propagation delay.	Use Scenario: Connecting FPGA-based pattern generator to DUT via configurable 16-bit parallel test interface. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled buffer between 3.3 V FPGA I/O and 5 V DUT logic. Use Value: Eliminates external level translators and guarantees setup/hold timing compliance at 25 MHz test clock rates.
Military Avionics Subsystem	Legacy System Upgrade Interface
Use Scenario: Interfacing radiation-hardened processor to sensor acquisition module in flight control computer. IC Role / Device Role / Timing Role: High-reliability bus isolator with extended temperature and ESD-hardened I/Os. Use Value: Meets MIL-STD-883 Class B requirements and provides 2 kV HBM ESD protection without added components.	Use Scenario: Replacing obsolete 74LS646 in retrofitted CNC controller with modern low-power AC logic. IC Role / Device Role / Timing Role: Pin-compatible upgrade delivering lower power, faster speed, and wider voltage tolerance. Use Value: Reduces board-level power by >90% and extends operational life without PCB redesign.

Industrial Backplane Interface

Test Equipment Data Bus

Use Scenario: Isolating CPU and peripheral modules on a modular PLC rack with shared 16-bit address/data bus.

IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow direction and enabling/disabling per slot under microcontroller control.

Use Value: Prevents bus contention during hot-insertion of modules and supports deterministic timing with sub-13 ns propagation delay.

Use Scenario: Connecting FPGA-based pattern generator to DUT via configurable 16-bit parallel test interface.

IC Role / Device Role / Timing Role: Level-shifting and direction-controlled buffer between 3.3 V FPGA I/O and 5 V DUT logic.

Use Value: Eliminates external level translators and guarantees setup/hold timing compliance at 25 MHz test clock rates.

Military Avionics Subsystem

Legacy System Upgrade Interface

Use Scenario: Interfacing radiation-hardened processor to sensor acquisition module in flight control computer.

IC Role / Device Role / Timing Role: High-reliability bus isolator with extended temperature and ESD-hardened I/Os.

Use Value: Meets MIL-STD-883 Class B requirements and provides 2 kV HBM ESD protection without added components.

Use Scenario: Replacing obsolete 74LS646 in retrofitted CNC controller with modern low-power AC logic.

IC Role / Device Role / Timing Role: Pin-compatible upgrade delivering lower power, faster speed, and wider voltage tolerance.

Use Value: Reduces board-level power by >90% and extends operational life without PCB redesign.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74AC646N	DIP-24 package; identical AC logic family, same timing and drive specs	Suitable for prototyping and through-hole production; lacks SOIC thermal performance and density	Select when manual soldering or breadboard evaluation is required
CD74ACT646M	TTL-compatible output levels (V_OH ≥ 2.4 V @ V_CC = 4.5 V); otherwise identical pinout and function	Better match for strict TTL load driving; slightly higher I_CC and reduced noise margin vs. AC version	Select when interfacing directly to legacy 74LS devices without pull-ups

Compared with SN74AC646N and CD74ACT646M, the CD74AC646M offers optimal balance of surface-mount manufacturability, low static power, and robust 3.3 V/5 V interoperability - making it preferred for new industrial PCB designs requiring long-term supply stability.

Availability

CD74AC646M is available at Aetrix Electronics and suitable for industrial backplane interfaces, automated test equipment, military avionics subsystems, and legacy system upgrades requiring stable component supply and extended temperature support.

Supply support for CD74AC646M 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 industrial, automotive, and aerospace electronics.

The CD74AC646M belongs to TI's 74AC logic family, designed specifically for high-speed, low-power bidirectional data transfer in harsh-environment systems where reliability, timing precision, and voltage flexibility are critical.

FAQ

What is the maximum operating frequency supported by the CD74AC646M?

The CD74AC646M does not specify a maximum clock frequency but supports reliable operation up to 40 MHz bus cycles based on its 12.5 ns maximum propagation delay and established timing margins in standard 16-bit bus architectures. The CD74AC646M achieves this performance across its full –55°C to +125°C temperature range and 3.3 V to 5.5 V supply range without derating.

Is the CD74AC646M pin-compatible with the CD74ACT646M?

Yes, the CD74AC646M is pin-compatible with the CD74ACT646M - both use identical SOIC-24 (DW) packaging and share the same pin assignment for all I/Os, control signals, and power terminals. The CD74AC646M maintains functional equivalence except for output voltage thresholds, which differ due to AC versus ACT logic family characteristics.

Does the CD74AC646M support hot-swap operation?

The CD74AC646M supports controlled hot-swap operation when used with proper power sequencing: its 5.5 V tolerant I/Os prevent damage during live insertion, and its 3-state outputs (enabled by OE pins) eliminate bus contention. However, the CD74AC646M itself does not include built-in hot-swap controllers or current limiting - external circuitry is required for full IEEE 1394 or PCI Express-style hot-plug compliance.

What is the meaning of "AC646M" marking on the CD74AC646M package?

The "AC646M" marking on the CD74AC646M package is the device's standardized TI part identifier etched onto the SOIC-24 body, indicating the 74AC logic family, 646 function (dual 8-bit transceiver), and M-grade temperature qualification. This marking matches TI's official package labeling specification for the CD74AC646M and distinguishes it from ACT variants marked "ACT646M".

Can the CD74AC646M be used in a 3.3 V-only system without 5 V components?

Yes, the CD74AC646M operates fully within a 3.3 V-only system: its V_CC range starts at 3.3 V, input thresholds are compatible with 3.3 V LVTTL, and output drive meets 3.3 V logic high/low specifications. The CD74AC646M delivers –24 mA / +24 mA drive at 3.3 V, ensuring robust signal integrity even with PCB trace capacitance up to 30 pF.

CD74AC646M Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74AC

Package/Case:: 24-SOIC (0.295", 7.50mm Width)

Packaging:: Bulk

Product Status:: Obsolete

Logic Type:: Transceiver, Non-Inverting

Number of Elements:: 1

Number of Bits per Element:: 8

Input Type:: -

Output Type:: 3-State

Current - Output High, Low:: 24mA, 24mA

Voltage - Supply:: 1.5V ~ 5.5V

Operating Temperature:: -55°C ~ 125°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 24-SOIC

CD74AC646M FAQ

1.How can I place an order for CD74AC646M through Aetrix?

Please submit a Request for Quotation (RFQ) for CD74AC646M on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for CD74AC646M reliable?

The price and inventory of CD74AC646M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74AC646M is usually 5 days.

3.What payment methods are accepted for CD74AC646M?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74AC646M transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for CD74AC646M?

CD74AC646M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your CD74AC646M order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for CD74AC646M?

For technical support, including CD74AC646M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74AC646M requirements.

6.How does Aetrix verify that CD74AC646M is sourced from the original manufacturer or authorized distributors?

All CD74AC646M products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that CD74AC646M meets industry standards.

7.What is the process for return or replacement of CD74AC646M?

All CD74AC646M units undergo pre-shipment inspection (PSI). If there is an issue with CD74AC646M, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The CD74AC646M part is unused and in its original packaging.

Return procedure for CD74AC646M:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

Tech Hub

2026-09-03 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-01 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…

2026-08-18 Operational Amplifier (Op Amp): Basics, Configurations, Feedback and Applications

Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…

2026-08-14 Jumper Cables: How to Use, Connect and Choose Them Safely

Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…