Texas Instruments CD74AC245E

Overview

CD74AC245E from Texas Instruments is an octal non-inverting three-state bidirectional bus transceiver in 20-pin PDIP packaging, operating from 1.5V to 5.5V with ±24mA output drive, 4ns typical propagation delay at 5V/25°C/50pF, and SCR-latchup-resistant CMOS logic - used for level-shifting and bidirectional data flow control between microcontroller buses and peripheral subsystems.

For engineers reviewing the CD74AC245E datasheet, CD74AC245E pinout, CD74AC245E application, or CD74AC245E equivalent, key selection criteria include its wide VCC range (1.5–5.5V), balanced noise immunity (30% of supply), 50Ω transmission-line drive capability, and compatibility with FAST™-fanout loads (15 ICs) in industrial and embedded bus interface designs.

Technical Context

The CD74AC245E implements a dual-bus bidirectional transceiver architecture controlled by DIR (direction) and OE (output enable) inputs. Its non-inverting logic path supports A-to-B or B-to-A data transfer depending on DIR state, while OE asserts high-impedance outputs when active high.

It uses Advanced CMOS Logic with buffered inputs, balanced propagation delays across all eight channels, and operates across –55°C to +125°C. The device features 10pF input capacitance, 15pF three-state output capacitance, and 57pF power dissipation capacitance - enabling predictable timing and low dynamic power in synchronous bus systems.

Key Specifications

Pinout & Package

CD74AC245E is supplied in a 20-pin plastic dual in-line package (PDIP, N package), body size 24.33mm × 6.35mm, total footprint 24.33mm × 9.4mm including leads. Pin 1 is marked by a notch or dot; pin 10 is GND, pin 20 is VCC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AC245N and 74LVC245APW, CD74AC245E uniquely supports full 1.5V–5.5V operation and extended temperature range, making it the only option among the three qualified for harsh-environment industrial and defense applications requiring guaranteed performance from –55°C to +125°C.

Availability

CD74AC245E is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and medical imaging data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74AC245E 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 delivering analog and embedded processing solutions, with over 90 years of innovation in precision logic, power management, and signal chain technologies.

The CD74AC245E belongs to TI's Advanced CMOS (AC) logic family, designed specifically for high-speed, low-power, mixed-voltage bus interfacing in industrial automation, test equipment, and mission-critical embedded systems.

FAQ

What is the maximum clock frequency supported by CD74AC245E in a synchronous bus application?

The CD74AC245E does not contain internal clocking circuitry and is not a clocked device. Its usable data rate depends on propagation delay and system layout: with 4ns typical tPLH/tPHL and proper termination, it reliably supports bidirectional data toggling up to ~100MHz on short PCB traces. System-level timing must account for worst-case 10.8ns max delay at 3V and 85°C per the datasheet switching characteristics table. For CD74AC245E, timing margin analysis should use actual measured tPLH/tPHL under operating VCC and temperature.

Can CD74AC245E operate at 1.8V supply voltage, and what are the guaranteed output drive levels?

Yes, CD74AC245E is fully specified down to 1.5V VCC. At 1.8V, VOH is guaranteed ≥1.4V (min) and VOL ≤0.1V (max) across –40°C to +85°C, with output drive current reduced to ±12mA (typical). This maintains >0.4V noise margin for 1.8V logic families. The ±24mA rating applies only at VCC ≥3V per the Electrical Characteristics table. CD74AC245E remains functional and compliant at 1.8V, but designers must verify load conditions against derated drive capability.

Is CD74AC245E pin-compatible with CD74ACT245E, and can they be interchanged on the same PCB?

Yes, CD74AC245E and CD74ACT245E share identical 20-pin PDIP mechanical footprint, pinout, and functional block diagram. However, they differ electrically: CD74ACT245E uses TTL-compatible input thresholds (VIH = 2.0V min, VIL = 0.8V max at 4.5V–5.5V) and has slightly slower propagation delay (2.7ns typ vs. 4ns typ at 5V). Interchange is possible only if the system's input logic levels and timing budget accommodate ACT-family thresholds and timing. CD74AC245E cannot directly replace CD74ACT245E in strict TTL-driven systems without validation.

What thermal considerations apply when operating CD74AC245E at maximum ambient temperature?

At maximum ambient temperature (+125°C), CD74AC245E's RθJA for PDIP (N) package is 69°C/W. With max ICC of 160µA and worst-case output switching, power dissipation remains <1mW - resulting in negligible junction temperature rise (<0.1°C). No heatsinking is required. However, PCB layout must maintain thermal relief: avoid large copper pours directly under the package, ensure GND and VCC traces are ≥0.3mm wide, and place the 0.1µF bypass capacitor within 2mm of pin 20. CD74AC245E's thermal design is inherently robust for extended-temperature operation.

Does CD74AC245E require external pull-up or pull-down resistors on DIR or OE pins in a typical application?

No, CD74AC245E does not require external biasing on DIR or OE. Its CMOS inputs have ±1µA max leakage (II) across –55°C to +125°C, so a clean logic-level signal from an MCU GPIO or dedicated control line is sufficient. Floating DIR or OE is strictly prohibited - uncontrolled states cause undefined bus behavior or contention. If control signals are inactive during power-up, use MCU firmware initialization or a simple RC reset network to guarantee known OE=HIGH (high-Z) and DIR=LOW during boot. CD74AC245E itself contains no internal pull resistors.