Texas Instruments CD74HC74E

Overview

CD74HC74E from Texas Instruments is a dual D-type positive-edge-triggered flip-flop with independent asynchronous clear and preset inputs per channel, operating across 2 V to 6 V supply, supporting –55°C to +125°C temperature range, and delivering ≤45 ns propagation delay at 6 V - used in clock division and momentary-to-toggle switch conversion circuits.

For engineers reviewing the CD74HC74E datasheet, CD74HC74E pinout, CD74HC74E application, or CD74HC74E equivalent, this page delivers verified functional mode definitions, timing constraints (tsu = 10 ns, th = 3 ns, fmax = 23 MHz at 6 V), thermal metrics (RθJA = 62.2 °C/W), and package-specific layout guidance for PDIP-14.

Technical Context

The CD74HC74E implements two fully independent CMOS D-flip-flops sharing no internal logic; each features separate asynchronous active-low PRE and CLR inputs, positive-edge-triggered CLK, and complementary Q/Q outputs. Its balanced push-pull output stage enables symmetrical sourcing/sinking (±25 mA) while maintaining rail-to-rail VOH/VOL compliance across voltage and temperature.

Timing behavior is strictly defined by setup (tsu ≥ 10 ns at 6 V), hold (th = 3 ns), and pulse width (tw ≥ 14 ns) requirements. Functional modes include synchronous data capture on clock edge, asynchronous set/reset overriding clock action, and metastability-limited transparent latch behavior only during invalid PRE/CLR transitions.

Key Specifications

Pinout & Package

CD74HC74E uses a 14-pin Plastic Dual In-line Package (PDIP) with nominal body size 19.30 mm × 6.40 mm, through-hole mounting, and NIPDAU lead finish compliant with RoHS.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC74E, SN74HC74N offers higher guaranteed clock frequency and lower dynamic power, while MC74HC74ANG provides second-source assurance with identical form-fit-function - both retain full compatibility with existing PDIP-14 footprints and timing margins.

Availability

CD74HC74E is available at Aetrix Electronics and suitable for industrial control panels, automotive body electronics, aerospace avionics modules, and test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC74E 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 50 years of innovation in high-reliability digital ICs.

The CD74HC74E belongs to TI's 74HC logic family - designed specifically for robust, low-power, wide-voltage-range combinatorial and sequential logic in harsh-environment applications.

FAQ

What is the maximum clock frequency supported by CD74HC74E?

The CD74HC74E guarantees operation up to 23 MHz at VCC = 6 V and TA = –55°C to +125°C, based on its specified maximum propagation delay (tpd = 45 ns) and timing requirements (tw = 14 ns). At 4.5 V, the limit drops to 20 MHz; at 2 V, it is 4 MHz. These values are measured under CL = 50 pF load and define the upper bound for reliable synchronous operation without setup/hold violations in the CD74HC74E.

Does CD74HC74E support asynchronous reset and set functionality?

Yes, the CD74HC74E provides independent asynchronous active-low preset (PRE) and clear (CLR) inputs for each of its two D-type flip-flops. When PRE is pulled LOW, the corresponding Q output goes HIGH immediately, overriding any clock or data activity. When CLR is pulled LOW, Q goes LOW regardless of other inputs. These functions operate independently per channel and take precedence over clocked data capture in the CD74HC74E.

What is the recommended bypass capacitor for CD74HC74E?

A 0.1 µF ceramic capacitor is recommended for bypassing the VCC pin of the CD74HC74E, placed physically adjacent to the device with short, low-inductance traces to GND. This value suppresses high-frequency supply noise generated by switching outputs and ensures stable operation across the full temperature and voltage range. For enhanced noise rejection, TI also recommends paralleling with a 1 µF capacitor - both must be located as close as possible to pins 14 (VCC) and 7 (GND) in the CD74HC74E layout.

Can unused inputs on CD74HC74E be left floating?

No, unused inputs on the CD74HC74E must never be left floating. Standard CMOS inputs have high impedance and undefined voltage states when unconnected, which can cause excessive current draw, oscillation, or unpredictable output behavior. All unused inputs - including PRE, CLR, D, and CLK - must be terminated to either VCC or GND via direct connection or pull-up/pull-down resistors (e.g., 10 kΩ). This requirement applies to both channels and is mandatory for reliable CD74HC74E operation.

What is the thermal resistance (RθJA) of CD74HC74E in its PDIP package?

The junction-to-ambient thermal resistance (RθJA) of the CD74HC74E in its 14-pin PDIP (N) package is 62.2 °C/W, as specified in the device's official datasheet (SCHS124E, Rev. May 2021). This value assumes standard JEDEC 2-layer board conditions and defines the temperature rise above ambient per watt of power dissipated. It is significantly lower than the SOIC version (133.6 °C/W), making the CD74HC74E more thermally robust in through-hole applications where airflow or heatsinking is limited.