Texas Instruments CD74HC257MT

Overview

CD74HC257MT from Texas Instruments is a quad 2-input multiplexer with three-state non-inverting outputs, designed for data routing and bus isolation in digital logic systems. It features 2V–6V operation, 12ns typical propagation delay at 5V/15pF, -55°C to +125°C operating range, and active-low output enable (OE) for high-impedance control. It is commonly used in register-to-bus data selection and function generation circuits.

For engineers reviewing the CD74HC257MT datasheet, CD74HC257MT pinout, CD74HC257MT application, or CD74HC257MT equivalent, key selection considerations include its SOIC-16 package, HC-series CMOS compatibility, three-state output behavior, wide temperature range, and precise timing specs under varying VCC and load conditions.

Technical Context

The CD74HC257MT implements four independent 2:1 multiplexers sharing a common select (S) and output enable (OE) input. Each channel routes either I0 or I1 to Y based on S state, with OE overriding all outputs to high-Z when asserted high. Its HC logic family ensures CMOS-level noise immunity (NIL/NIH = 30% of VCC) and low static power consumption.

Propagation delays are characterized across VCC (2V–6V) and load capacitance (15pF/50pF), with tPLH/tPHL = 12ns typ. at 5V/15pF. Input rise/fall time limits (e.g., 400ns max at 6V) and defined unit-load inputs (S = 3 loads, OE = 0.6 loads) support predictable fanout and bus loading analysis in mixed-logic designs.

Key Specifications

Pinout & Package

CD74HC257MT is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package, surface-mount compatible with standard reflow profiles (MSL Level-1, 260°C peak). The body width is 3.9mm, lead pitch is 1.27mm, and total package dimensions are 9.9mm × 3.9mm × 1.75mm (L × W × H).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2-input multiplexer applications.

Compared with SN74HC257N and CD74HCT257MT, CD74HC257MT offers broader supply flexibility (2V–6V), superior noise immunity, and surface-mount compatibility - making it optimal for modern mixed-voltage embedded controllers and high-reliability industrial modules.

Availability

CD74HC257MT is available at Aetrix Electronics and suitable for industrial automation, aerospace data acquisition, and test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC257MT 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 decades of heritage in high-reliability logic families.

The CD74HC257MT belongs to TI's High-Speed CMOS (HC) logic product line, engineered for low-power, wide-voltage digital interfacing in harsh-environment applications demanding extended temperature operation and noise resilience.

FAQ

What is the maximum clock/data rate supported by CD74HC257MT?

The CD74HC257MT does not operate on a clock; it is combinatorial logic. Its 12ns typical propagation delay at 5V/15pF supports data switching up to ~30 MHz in synchronous systems. Maximum usable frequency depends on load capacitance, supply voltage, and board layout - actual timing must be verified using worst-case values from the switching specifications table in the datasheet for CD74HC257MT.

Can CD74HC257MT interface directly with 3.3V microcontrollers?

Yes. CD74HC257MT operates from 2V to 6V and has CMOS-compatible input thresholds (VIH ≥ 1.5V at 2V VCC, ≥3.15V at 4.5V). When powered at 3.3V, its VIH(min) = 2.31V and VIL(max) = 0.99V - fully compatible with standard 3.3V GPIO outputs. Outputs swing rail-to-rail, ensuring clean logic levels for downstream 3.3V receivers.

Is CD74HC257MT pin-compatible with CD74HCT257MT?

Yes - CD74HC257MT and CD74HCT257MT share identical SOIC-16 pinout, pin functions, and mechanical footprint. However, they differ electrically: CD74HC257MT supports 2V–6V operation and CMOS input thresholds, while CD74HCT257MT is limited to 4.5V–5.5V and accepts TTL-level inputs. Swapping requires verifying supply voltage and driver compatibility.

What happens to outputs when OE is HIGH on CD74HC257MT?

When OE is driven HIGH, all four outputs (1Y–4Y) enter a high-impedance (Hi-Z) state regardless of S or input states - effectively disconnecting them from the bus. This behavior is confirmed in the truth table and functional description of CD74HC257MT. Leakage current in Hi-Z mode is ≤±10µA over full temperature range, ensuring minimal bus loading during disable.

Does CD74HC257MT require external pull-up or pull-down resistors on inputs?

No - CD74HC257MT inputs have no internal termination and exhibit ≤±1µA leakage (II), so floating inputs are electrically unstable. External pull-up or pull-down resistors are required for unused inputs (e.g., unconnected I0/I1 pins) to prevent oscillation, increased ICC, or erratic output behavior. Recommended values are 10kΩ–100kΩ, tied to VCC or GND per signal intent in the CD74HC257MT application circuit.