Texas Instruments CD74HCT74ME4

Overview

CD74HCT74ME4 from Texas Instruments is a dual D-type positive-edge-triggered flip-flop with independent asynchronous clear and preset inputs per channel, operating across 4.5 V to 5.5 V supply, supporting clock frequencies up to 25 MHz at –40°C to +85°C, and delivering balanced CMOS push-pull outputs for reliable digital state storage in synchronous logic systems.

For engineers reviewing the CD74HCT74ME4 datasheet, CD74HCT74ME4 pinout, CD74HCT74ME4 application, or CD74HCT74ME4 equivalent, key selection considerations include its 14-pin SOIC package, dual-channel edge-triggered behavior, guaranteed setup/hold timing (15 ns / 3 ns at 4.5 V), low-power HCT logic compatibility with TTL input thresholds, and operation within industrial temperature range.

Technical Context

This device implements two independent D-type latches synchronized to the rising edge of CLK, each with active-low asynchronous PRE and CLR enabling immediate state forcing regardless of clock phase. Its HCT logic family ensures TTL-compatible input voltage thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 4.5 V) while maintaining CMOS output drive strength and low quiescent current.

Each channel supports fanout of ≥10 LSTTL loads, exhibits propagation delay of 44 ns (typical, CL = 50 pF, VCC = 4.5 V), and maintains stable operation under fast input transitions (tr/tf ≤ 500 ns). The internal structure includes clamped CMOS inputs with IIK ≤ ±20 mA and balanced push-pull outputs capable of sourcing/sinking ±4 mA (VOH/VOL guaranteed at 4.5 V).

Key Specifications

Pinout & Package

CD74HCT74ME4 is housed in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated PCB assembly and reflow soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual D-type flip-flop applications.

Compared with SN74HCT74DR, CD74HCT74ME4 offers verified industrial-temperature performance at lower cost, while CD74HC74M96 provides broader supply flexibility but lacks TTL input compatibility - making CD74HCT74ME4 optimal for cost-sensitive 5 V industrial control where legacy interface assurance is required.

Availability

CD74HCT74ME4 is available at Aetrix Electronics and suitable for industrial automation, motor control, and embedded instrumentation requiring stable component supply, long-term production continuity, and RoHS-compliant packaging.

Supply support for CD74HCT74ME4 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 for industrial, automotive, and communications markets.

The CD74HCT74ME4 belongs to TI's HCT logic family, engineered to bridge TTL and CMOS domains with guaranteed input compatibility, low power, and robust noise immunity for industrial control and instrumentation systems.

FAQ

What is the maximum clock frequency supported by CD74HCT74ME4 across its full temperature range?

CD74HCT74ME4 guarantees operation up to 25 MHz at TA = –40°C to +85°C, as confirmed in Section 6.5 of the TI datasheet (SCHS409). At 4.5 V supply, the minimum clock period is 40 ns, corresponding to 25 MHz. Performance degrades slightly at temperature extremes - 20 MHz at –55°C and +125°C - but CD74HCT74ME4 is rated specifically for the industrial range where 25 MHz is fully assured. This makes CD74HCT74ME4 suitable for real-time control loops and moderate-speed digital interfaces.

Does CD74HCT74ME4 support direct connection to standard TTL logic inputs?

Yes, CD74HCT74ME4 is explicitly designed for TTL compatibility: its input thresholds meet VIH ≥ 2.0 V and VIL ≤ 0.8 V at VCC = 4.5 V, matching standard LS-TTL specifications. This allows CD74HCT74ME4 to accept outputs from 74LSxx devices without level-shifting circuitry. Unlike HC variants, HCT logic ensures reliable recognition of TTL voltage levels, making CD74HCT74ME4 ideal for mixed-technology upgrades or legacy system integration where CD74HCT74ME4 replaces obsolete 74LS74 components.

How should unused inputs be handled on CD74HCT74ME4 to ensure stable operation?

All unused inputs on CD74HCT74ME4 - including PRE, CLR, D, and CLK for inactive channels - must be terminated to a defined logic level. TI recommends tying them directly to VCC or GND via low-impedance connections; pull-up/pull-down resistors (e.g., 10 kΩ) are acceptable if dynamic control is needed later. Floating inputs risk oscillation, increased ICC, and unpredictable output states due to CMOS input sensitivity. For example, an unconnected CLR pin could drift toward threshold and cause unintended resets - a critical failure mode in safety-related CD74HCT74ME4 deployments.

Can CD74HCT74ME4 be used to build a divide-by-4 counter, and what is the recommended configuration?

Yes, CD74HCT74ME4 can implement a synchronous divide-by-4 counter using both internal flip-flops. Connect Channel 1 CLK to the input clock, tie Channel 1 D to Q̅1, then feed Channel 1 Q to Channel 2 CLK. Tie Channel 2 D to Q̅2. This cascades two divide-by-2 stages, yielding Q2 as fIN/4 with 50% duty cycle. Propagation delays accumulate (tpd ≈ 88 ns total), limiting max input frequency to ~11 MHz for reliable operation - well within CD74HCT74ME4's 25 MHz rating at nominal conditions. No external gates or feedback resistors are required.

Is CD74HCT74ME4 pin-compatible with CD74HC74M96, and what design changes are needed for substitution?

No, CD74HCT74ME4 is not pin-compatible with CD74HC74M96 in functional terms despite identical 14-pin SOIC packaging and pinout. While physical layout matches, CD74HC74M96 uses HCMOS input thresholds (VIH = 3.15 V min at VCC = 4.5 V), incompatible with TTL-level drivers. Substituting CD74HC74M96 for CD74HCT74ME4 risks logic misreads unless all upstream signals meet HCMOS thresholds. To retain functionality, redesign input buffering or verify source logic family - CD74HCT74ME4 remains the correct choice when interfacing with 74LS, 74F, or microcontroller GPIOs lacking rail-to-rail swing.