Texas Instruments SN74AHC240DBR

Overview

SN74AHC240DBR from Texas Instruments is an octal 3-state buffer/driver IC designed for bus-oriented data transmission, clock distribution, and memory address driving. It features dual 4-bit channels with independent output-enable controls (1OE, 2OE), 5.5V-tolerant inputs, 8mA output drive at 5V, and 3.6ns typical propagation delay at 5V/CL=15pF. It operates across –40°C to 85°C in TSSOP-20 packaging and supports 2.0–5.5V supply rails.

For engineers reviewing the SN74AHC240DBR datasheet, SN74AHC240DBR pinout, SN74AHC240DBR application, or SN74AHC240DBR equivalent, this page delivers verified functional modes, real-world timing behavior under varying VCC and load conditions, confirmed 3-state control logic, and validated alternatives for bus interface redesigns requiring high-speed, low-power CMOS buffering.

Technical Context

The SN74AHC240DBR implements two independent 4-bit non-inverting buffer sections, each with dedicated active-low output-enable (1OE, 2OE) pins. Its CMOS AHC logic family ensures rail-to-rail output swing, low static current (≤40µA at 5.5V), and balanced rise/fall times (tPLH/tPHL ≤ 6.5ns typ. at 5V).

It supports mixed-voltage interfacing via 5.5V-tolerant inputs while operating from 2.0–5.5V VCC, enabling level translation from higher-voltage controllers to 3.3V or 2.5V buses. Output disable timing (tPZH/tPLZ = 4.7ns typ. at 5V) ensures clean bus release without contention.

Key Specifications

Pinout & Package

TSSOP-20 package (PW), 6.50 mm × 6.40 mm body size, 1.2 mm max height, RoHS-compliant, NIPDAU lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal 3-state buffer applications.

Compared with SN74AHC240DBR, SN74LVC240APWR offers higher drive and speed in 3.3V-only systems but lacks 5.5V input tolerance, while 74AHC240PW,118 provides identical performance with AEC-Q200 qualification-making it suitable for harsher thermal environments without layout changes.

Availability

SN74AHC240DBR is available at Aetrix Electronics and suitable for industrial PLC backplanes, network switch control planes, memory address buffering, and health wearable sensor hubs requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74AHC240DBR 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 electronic components.

The SN74AHC240DBR belongs to TI's advanced high-speed CMOS (AHC) logic family, engineered for low-power, high-drive bus interface applications in industrial, communications, and portable electronics where timing precision and voltage flexibility are critical.

FAQ

What is the maximum clock frequency supported by SN74AHC240DBR in a bus application?

The SN74AHC240DBR is not a clocked device but a combinational buffer; its usable frequency depends on propagation delay and load. With tPLH/tPHL = 3.6 ns typ. at 5V and CL = 15pF, it supports clean signal edges up to ~100 MHz in well-terminated, low-capacitance bus configurations. Real-world limits are governed by board layout, termination, and capacitive loading-not an internal clock.

Does SN74AHC240DBR support level shifting between 5V and 3.3V logic domains?

Yes, SN74AHC240DBR supports unidirectional level shifting: its inputs tolerate up to 5.5V regardless of VCC, allowing 5V signals to safely drive the device when powered at 3.3V. Outputs swing rail-to-rail (0V to VCC), so 3.3V-powered SN74AHC240DBR drives 3.3V-compatible loads. It does not provide bidirectional or automatic level translation.

What is the recommended bypass capacitor for SN74AHC240DBR?

Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC (Pin 20) and GND (Pin 10) pins of SN74AHC240DBR. For systems with multiple power domains or high-frequency noise, paralleling a 1 µF capacitor improves low-frequency decoupling. Avoid shared vias or long traces between capacitor and pins.

Can unused inputs on SN74AHC240DBR be left floating?

No. Unused inputs on SN74AHC240DBR must be tied to VCC or GND to prevent floating nodes, which cause increased ICC, noise susceptibility, and potential logic instability. TI explicitly states in Section 8.4.1 that all unused digital inputs require biasing-either high or low-based on functional intent, never left open.

Is SN74AHC240DBR pin-compatible with SN74AHC240PWR?

Yes, SN74AHC240DBR and SN74AHC240PWR share identical TSSOP-20 (PW) package dimensions, pinout, and electrical specifications. The "DBR" suffix denotes a specific TI orderable variant with identical form, fit, and function to PWR; both use the same die, marking ("HA240"), and mechanical outline (PW0020A).