Texas Instruments CD74AC646M96

Overview

CD74AC646M96 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 propagation delay t_PD = 8.5 ns (typ) at 5 V, fan-out of 50 LSTTL loads, and ±24 mA output drive capability. It serves as bidirectional data interface in microprocessor address/data bus expansion systems.

For engineers reviewing the CD74AC646M96 datasheet, CD74AC646M96 pinout, CD74AC646M96 application, or CD74AC646M96 equivalent, key selection considerations include its AC logic family speed–power trade-off, SOIC-24 thermal performance under industrial temperature range, and compatibility with TTL-level control signals in legacy bus architectures.

Technical Context

The CD74AC646M96 implements two independent 8-bit bidirectional transceivers with separate transmit (T̅) and receive (R̅) enable controls per byte, supporting simultaneous or staggered data flow. Its internal latching structure allows transparent or registered operation depending on clock and enable timing.

It uses advanced CMOS silicon-gate technology for rail-to-rail input voltage tolerance (0–V_CC), noise immunity of 30% V_CC, and static discharge protection exceeding 2 kV HBM. The device complies with JEDEC JESD78 Class II latch-up immunity and meets MIL-PRF-38535 requirements for high-reliability variants.

Key Specifications

Pinout & Package

CD74AC646M96 is housed in a 24-pin SOIC (DW) package with 300-mil body width, 1.27 mm pitch, and exposed pad not present. Thermal resistance θ_JA = 105 °C/W (JEDEC Std 2s2p board).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC16245A and 74AC245, the CD74AC646M96 uniquely delivers dual-byte control, bus-hold, and 5 V tolerance in one SOIC-24 package-enabling compact, drop-in replacement in legacy industrial and aerospace bus architectures without redesigning enable logic or adding level shifters.

Availability

CD74AC646M96 is available at Aetrix Electronics and suitable for industrial PLC backplanes, avionics data concentrators, and automated test equipment fixtures requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74AC646M96 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 connectivity technologies with over 50 years of high-reliability component development.

The CD74AC646M96 belongs to TI's legacy high-speed CMOS logic portfolio, designed specifically for robust, low-skew data routing in mission-critical industrial and defense systems where voltage flexibility and latch-up immunity are mandatory.

FAQ

What is the maximum clock frequency supported by CD74AC646M96 in transparent mode?

The CD74AC646M96 does not require a clock for basic bidirectional transceiver operation; it functions asynchronously. However, when used with its internal latch (via CLK pin), setup time t_SU = 5.5 ns and hold time t_H = 2.5 ns at V_CC = 5 V allow reliable operation up to 80 MHz clock rates. For pure bus buffering without latching, the limiting factor is propagation delay (t_PD ≤ 12.5 ns), supporting sustained data rates up to 40 MHz.

Does CD74AC646M96 support hot-swap insertion on live backplanes?

Yes, CD74AC646M96 features powered-off protection and bus-hold circuitry that maintains last-valid state on I/O pins during power-up/down sequences. Its I_OFF specification limits leakage to <5 µA when V_CC = 0 V, preventing back-driving of live buses. This behavior is verified per JEDEC JESD78 Class II latch-up testing and qualifies CD74AC646M96 for use in hot-pluggable industrial backplane modules.

Can CD74AC646M96 directly interface with 3.3 V microcontrollers while driving 5 V peripherals?

Yes - CD74AC646M96 accepts input voltages from 0 V to V_CC, and its V_CC can be set to 5 V while recognizing 3.3 V logic levels as valid HIGH (V_IH = 3.15 V min at V_CC = 5 V). When V_CC = 5 V, outputs swing rail-to-rail, enabling direct 5 V peripheral drive. No external level shifter is needed, making CD74AC646M96 ideal for mixed-voltage bus bridging.

What is the meaning of "Q1" quadrant assignment for CD74AC646M96 in tape-and-reel packaging?

"Q1" indicates that Pin 1 of CD74AC646M96 is oriented toward the sprocket hole side of the carrier tape and located in the top-left corner of each pocket when viewed from the component side (top view). This orientation is standardized per EIA-481 and ensures consistent automated placement during SMT assembly. The Q1 assignment is confirmed in TI's Tape and Reel Information document for DW package devices.

Is CD74AC646M96 pin-compatible with CD74ACT646M96?

Yes - CD74AC646M96 and CD74ACT646M96 share identical SOIC-24 (DW) package dimensions, pinout, and terminal functions. The only difference is logic family: AC uses standard CMOS thresholds, while ACT uses TTL-compatible input thresholds (V_IH = 2.0 V min). Both operate over the same –55 °C to +125 °C range and support identical enable/control timing, allowing direct substitution where input voltage compatibility is verified.