CD74HC74E-NG Equivalent & Substitute Parts

Part Overview

The CD74HC74E-NG is a dual D-type flip-flop logic integrated circuit manufactured by Texas Instruments, housed in a 14-DIP through-hole package. This device provides two independent 1-bit D-type flip-flops with set and reset functionality, operating at a maximum clock frequency of 35 MHz with a propagation delay of 34 ns at 6V with 50 pF load.

The CD74HC74E-NG is classified as obsolete. Identifying equivalent substitute parts is necessary to maintain design continuity, ensure supply chain availability, and leverage active product lines with improved electrical performance characteristics while maintaining functional compatibility.

Substiute Parts

CD74HC74E-NG

Texas InstrumentsIn Stock: 957CD74HC74E-NG Datasheet

Current PartRFQ

SN74HCS74BQAR

Texas InstrumentsIn Stock: 8234SN74HCS74BQAR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the CD74HC74E-NG is determined by the following critical parameters that must remain constant or compatible:

Functional Requirements:

• Dual D-type flip-flop configuration (2 elements, 1 bit per element)
• Set (Preset) and Reset functionality
• Complementary output type
• Positive edge trigger mechanism

Electrical Compatibility:

• Supply voltage range: 2V to 6V (must encompass or match the original range)
• Output current capability: minimum 5.2 mA per output
• Quiescent current: must not exceed design budget constraints
• Input capacitance: affects signal integrity in existing circuits

Timing Characteristics:

• Propagation delay must be equal to or faster than 34 ns at specified conditions
• Clock frequency capability must meet or exceed 35 MHz operational requirements

Environmental & Compliance:

• Operating temperature range must cover -55°C to 125°C or be compatible with application requirements
• RoHS3 compliance required for regulatory alignment

The substitute part SN74HCS74BQAR meets all functional and electrical requirements while offering improved performance metrics and active product status. The primary trade-off involves package type transition from through-hole (14-DIP) to surface-mount (14-QFN), which requires PCB redesign considerations.

Parameter Comparison

Engineering Selection Recommendations

Functional Compatibility: The SN74HCS74BQAR is functionally equivalent to the CD74HC74E-NG. Both devices implement identical dual D-type flip-flop logic with set/reset control and complementary outputs. All logic-level specifications and timing relationships are preserved.

Performance Enhancement: The SN74HCS74BQAR operates at 105 MHz maximum clock frequency compared to 35 MHz for the CD74HC74E-NG, providing a 3x performance margin. Propagation delay is reduced from 34 ns to 15 ns, improving timing margins in synchronous circuits. Output drive current increases from 5.2 mA to 7.8 mA, enhancing fan-out capability. Quiescent current decreases from 4 µA to 2 µA, reducing power consumption in standby states.

Product Status & Supply: The CD74HC74E-NG is obsolete with no active manufacturing. The SN74HCS74BQAR is in active production status, ensuring long-term availability and supply chain stability. Both parts maintain ROHS3 compliance for regulatory alignment.

Temperature Range Consideration: The CD74HC74E-NG operates from -55°C to 125°C, while the SN74HCS74BQAR operates from -40°C to 125°C. Applications requiring operation below -40°C must retain the original part or identify alternative solutions.

Package Transition Impact: Substitution requires transition from 14-DIP through-hole to 14-QFN surface-mount package. This necessitates PCB layout redesign, including footprint modification, trace routing adjustments, and thermal management considerations for the exposed pad. Assembly process changes from through-hole insertion to surface-mount reflow soldering are required.

Frequently Asked Questions (FAQ)

Q: Can the SN74HCS74BQAR directly replace the CD74HC74E-NG without circuit modifications?

A: Functional and electrical substitution is valid. However, package geometry differs fundamentally: 14-DIP (through-hole, 0.300" width, 7.62 mm pitch) versus 14-QFN (surface-mount, 3x2.5 mm). Direct socket replacement is not possible. PCB redesign is required to accommodate the new package footprint and assembly process.

Q: Are the logic signal levels and timing compatible between these parts?

A: Yes. Both parts operate with identical supply voltage range (2V to 6V), logic threshold levels, and complementary output configuration. The SN74HCS74BQAR provides faster propagation delay (15 ns vs. 34 ns), which improves timing margins and is backward-compatible with designs expecting the slower original part.

Q: What is the impact of the lower operating temperature minimum (-40°C vs. -55°C) for the substitute?

A: Applications operating below -40°C ambient temperature cannot use the SN74HCS74BQAR. If the design requires -55°C operation, the original CD74HC74E-NG specification must be maintained, or alternative parts with matching temperature range must be identified. Most commercial and industrial applications operate within the -40°C to 125°C range.

Q: Does the reduced quiescent current (2 µA vs. 4 µA) provide design benefits?

A: Yes. Lower quiescent current reduces standby power consumption by 50%, beneficial for battery-powered or low-power applications. This is a performance improvement with no negative impact on existing designs.

Q: How does the increased output current (7.8 mA vs. 5.2 mA) affect circuit design?

A: Higher output drive capability increases fan-out capacity and reduces output impedance, improving signal integrity and noise margins. This is a performance enhancement compatible with all designs expecting the original 5.2 mA specification.

Q: What assembly and manufacturing changes are required for the package transition?

A: Through-hole assembly (14-DIP) transitions to surface-mount assembly (14-QFN). This requires: PCB footprint redesign with appropriate pad dimensions and spacing for QFN package; reflow soldering process instead of wave soldering; thermal management of the exposed pad; updated assembly documentation and test procedures. Manufacturing lead times and costs may differ between through-hole and surface-mount processes.

Q: Is the SN74HCS74BQAR available in tape-and-reel packaging for automated assembly?

A: Yes. The SN74HCS74BQAR is supplied in Tape & Reel (TR) packaging, standard for surface-mount automated assembly processes. The CD74HC74E-NG through-hole package typically uses tube or tray packaging for manual or semi-automated insertion.

Q: Are there any signal integrity differences between the 10 pF input capacitance (original) and 5 pF (substitute)?

A: Lower input capacitance (5 pF) reduces loading on driving circuits, improving signal rise/fall times and reducing power consumption in the driving stage. This is a performance improvement with no negative compatibility impact.

Q: What certifications and compliance standards apply to both parts?

A: Both the CD74HC74E-NG and SN74HCS74BQAR are ROHS3 compliant. The SN74HCS74BQAR carries additional certifications: REACH Unaffected status and ECCN EAR99 classification. Moisture Sensitivity Level (MSL) is 1 (Unlimited) for the substitute, indicating minimal moisture absorption risk during storage and handling.