Texas Instruments CD74HCT157MT

Overview

CD74HCT157MT from Texas Instruments is a quad 2-input non-inverting multiplexer IC used for data routing in digital logic systems. It features active-low enable (E), common select (S), 16-pin SOIC package, -55°C to +125°C operating temperature, and TTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2.0 V at VCC = 4.5–5.5 V). It is commonly deployed in register-to-bus data selection and function generation circuits.

For engineers reviewing the CD74HCT157MT datasheet, CD74HCT157MT pinout, CD74HCT157MT application, or CD74HCT157MT equivalent, key selection considerations include its HCT logic family compatibility with LSTTL inputs, guaranteed operation across extended temperature range, propagation delay of 25–41 ns (CL = 50 pF), and SOIC-16 packaging for surface-mount industrial control designs.

Technical Context

The CD74HCT157MT implements four independent 2:1 multiplexers sharing one common select line (S) and one active-low enable input (E). When E is high, all outputs (1Y–4Y) are forced low regardless of S or data inputs - enabling clean bus isolation.

Its HCT logic family ensures direct interface with legacy LSTTL outputs while maintaining CMOS power efficiency. Input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and output drive capability (±25 mA per pin) support robust noise margin and fanout to 10 LSTTL loads over full temperature range.

Key Specifications

Pinout & Package

CD74HCT157MT is housed in a 16-pin Small Outline Integrated Circuit (SOIC) package with standard 1.27 mm pitch and JEDEC MS-012AC outline. Pin 1 is located at the top-left corner when viewed from the top with the marking side up and notch or dot oriented left.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HCT157MT, SN74HCT157DR offers assured long-term availability and updated process control, while CD74HCT157M96 provides identical performance in high-volume tape-and-reel form - both eliminate obsolescence risk present in the discontinued MT suffix variant.

Availability

CD74HCT157MT is available at Aetrix Electronics and suitable for industrial control systems, aerospace telemetry interfaces, and automotive engine management units requiring stable component supply across extended temperature ranges.

Supply support for CD74HCT157MT 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 high-reliability component heritage.

The CD74HCT157MT belongs to TI's legacy CD74HCT high-speed CMOS logic family, designed specifically for drop-in replacement of 74LS devices in demanding environments where wide temperature operation and TTL compatibility are essential.

FAQ

Is CD74HCT157MT still in active production?

No, CD74HCT157MT is obsolete per Texas Instruments' official packaging addendum. It is no longer manufactured or stocked by TI. However, Aetrix Electronics maintains limited legacy inventory with full traceability and supports continuity planning for existing designs reliant on this specific SOIC-16 small-reel variant.

What is the maximum clock/data rate supported by CD74HCT157MT?

CD74HCT157MT does not operate on a clock; it is combinational logic. Its usable data rate depends on propagation delay and system setup/hold timing. With tPLH/tPHL ≤ 41 ns (max) at VCC = 4.5 V and CL = 50 pF, it reliably supports data switching up to approximately 10–12 MHz in well-designed PCB layouts with controlled trace impedance and proper decoupling.

Can CD74HCT157MT interface directly with 3.3 V logic?

No - CD74HCT157MT requires VCC = 4.5–5.5 V and has TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). While 3.3 V outputs may meet VIH min under some conditions, they violate the 2.0 V minimum guarantee and risk unreliable operation. A level-shifter or buffer such as SN74LVC1T45 is required for robust 3.3 V ↔ 5 V interfacing.

Does CD74HCT157MT have ESD protection diodes on its inputs?

Yes - CD74HCT157MT includes internal clamp diodes on all inputs and outputs, rated for ±20 mA DC input/output diode current per Absolute Maximum Ratings. Users must observe proper handling procedures and avoid exceeding -0.5 V or VCC + 0.5 V on any pin to prevent damage, as stated in the TI datasheet caution notice.

How does the enable (E) pin behavior differ between CD74HCT157MT and CD74HC157 variants?

In CD74HCT157MT, E is active-low and forces all outputs (1Y–4Y) low when high. In CD74HC157, E is also active-low but forces outputs to high-impedance (Hi-Z) when disabled - a fundamental functional difference. CD74HCT157MT's forced-low behavior provides defined bus state during disable, unlike HC's tri-state capability.