Texas Instruments CD74HCT240M

Overview

CD74HCT240M from Texas Instruments is an inverting octal buffer/line driver with three-state outputs and dual active-low output enables, designed for bidirectional bus interfacing in 5-V TTL-compatible digital systems. It delivers 8ns typical propagation delay at V_CC = 5 V, CL = 15 pF, supports ±25 mA output drive, operates across –55°C to +125°C, and features buffered inputs for noise immunity in industrial control backplanes.

For engineers reviewing the CD74HCT240M datasheet, CD74HCT240M pinout, CD74HCT240M application, or CD74HCT240M equivalent, this page provides verified functional role, thermal derating guidance, bus-driver-level current capability, LSTTL-load fanout (15), and HCT-specific input threshold compatibility (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) critical for legacy system upgrades and mixed-voltage interface design.

Technical Context

The CD74HCT240M implements two independent 4-bit inverting buffer sections, each controlled by its own active-low output enable (1OE, 2OE). Its CMOS process ensures low static power consumption while maintaining TTL-compatible input thresholds and robust output drive-enabling direct replacement of LS-TTL buffers without level-shifting circuitry.

All logic transitions are internally balanced to minimize ground bounce and skew between channels. The device's three-state architecture allows high-impedance output disable during bus arbitration, with guaranteed t_PLZ/t_PZH ≤ 45 ns (–55°C to +125°C) and t_PZL/t_PHZ ≤ 45 ns under worst-case conditions, supporting reliable hot-swap and dynamic bus sharing.

Key Specifications

Pinout & Package

CD74HCT240M is supplied in a 20-pin SOIC (Small Outline Integrated Circuit) package with nominal body dimensions of 12.80 mm × 7.50 mm and standard JEDEC MS-013 footprint. This surface-mount package supports automated assembly and offers improved thermal performance over PDIP variants.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal inverting buffer applications.

Compared with SN74HCT240N and 74ACT240SCX, CD74HCT240M uniquely combines SOIC packaging, –55°C to +125°C qualification, and precise TTL-compatible thresholds-making it the sole option for space-constrained, high-reliability industrial and automotive applications demanding full-spec operation across extreme temperatures.

Availability

CD74HCT240M is available at Aetrix Electronics and suitable for industrial backplane interfaces, automotive ECU data multiplexing, legacy system bus extension, and programmable logic interface applications requiring stable component supply, long-term lifecycle support, and guaranteed extended-temperature performance.

Supply support for CD74HCT240M 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 decades of expertise in logic IC design, manufacturing, and automotive-grade qualification.

The CD74HCT240M belongs to TI's High-Speed CMOS (HCT) logic family, engineered specifically for seamless 5-V TTL-to-CMOS interfacing in industrial, automotive, and avionics systems where reliability, temperature resilience, and input compatibility are non-negotiable.

FAQ

What is the maximum output current per pin for CD74HCT240M?

The CD74HCT240M supports ±25 mA DC output current per pin under recommended operating conditions (V_CC = 4.5 V to 5.5 V, T_A = –55°C to +125°C). This value is specified in the Electrical Characteristics table for '240 devices and enables direct driving of 15 LSTTL loads without external buffering. Exceeding this limit risks parametric shift or long-term reliability degradation.

Does CD74HCT240M support 3.3-V input logic levels?

No, CD74HCT240M does not reliably recognize 3.3-V logic levels as valid inputs. Its HCT input thresholds require V_IH ≥ 2.0 V and V_IL ≤ 0.8 V at V_CC = 4.5–5.5 V. A 3.3-V high signal falls below the minimum V_IH, risking indeterminate switching. For mixed-voltage systems, use a level translator or select a 3.3-V–tolerant logic family instead of CD74HCT240M.

Can CD74HCT240M replace CD74HC240 in existing designs?

CD74HCT240M can replace CD74HC240 only if the system uses 5-V TTL-compatible inputs and requires identical inverting three-state behavior. However, CD74HCT240M has narrower V_CC range (4.5–5.5 V vs. 2–6 V) and different input thresholds. Substitution may cause failure in 3.3-V or wide-supply systems. Always verify V_CC, input source type, and timing margins before swapping CD74HCT240M into a CD74HC240 design.

What is the thermal resistance (R_θJA) of CD74HCT240M in SOIC package?

The junction-to-ambient thermal resistance (R_θJA) for CD74HCT240M in the SOIC (M) package is 109.1°C/W, as specified in the Thermal Information table. This value assumes standard JEDEC 2-layer board conditions. Actual thermal performance depends on PCB copper area, airflow, and nearby heat sources-designers should validate junction temperature using T_J = T_A + (P_D × R_θJA) under worst-case load.

How are the output enable pins configured on CD74HCT240M?

CD74HCT240M features two active-low output enables: 1OE (pin 10) controls outputs Y1–Y4, and 2OE (pin 19) controls outputs Y5–Y8. Both must be driven low to activate their respective 4-bit groups; either enable held high places its associated outputs in high-impedance state. This dual-enable architecture supports segmented bus control without external logic.