Part A
74HC74D
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 3058 PCS
- Package
- SOIC-14
- Series
- Logic - Flip Flops
Replacement verdict
Not a drop-in replacement
The 74HC74D and 74HC7403D,518 are not functionally interchangeable. The 74HC74D is a dual D-type flip-flop with set and reset, while the 74HC7403D,518 is a hex D-type flip-flop with a completely different channel count, pinout, and package configuration. Substitution requires a full circuit redesign and cannot be treated as a drop-in replacement.
Different channel count
Different logic function
Different pinout
Different package type
Parts at a glance
Part B
74HC7403D,518
NXP Hoa Kỳ Inc.
- Lifecycle
- Active
- Stock
- 7818 PCS
- Package
- SOIC-16
- Series
- Logic - FIFOs Memory
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC74D | 74HC7403D,518 | Why it matters |
|---|---|---|---|
| Logic Function | Dual D-Type Flip-Flop with Set and Reset | Quad 2-Input NOR Gate | The fundamental logic function determines whether the parts are functionally interchangeable in a circuit. |
| Number of Circuits | 2 | 4 | The number of independent logic elements affects how many signals can be processed per package. |
| Number of Inputs per Circuit | 1 (D input) | 2 | Input count per element determines the logic operation and wiring requirements. |
| Number of Outputs per Circuit | 2 (Q and Qbar) | 1 | Output configuration affects signal routing and whether complementary outputs are available. |
| Clock Input | Yes (edge-triggered) | No | Clock input determines whether the device is sequential (flip-flop) or combinational (gate) logic. |
| Set/Reset Capability | Yes (asynchronous) | No | Set and reset pins allow direct control of output state independent of clock, which is essential for initialization. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | The operating voltage range must match the system supply for reliable operation. |
| Logic Family | 74HC | 74HC | Same logic family ensures compatible input/output voltage thresholds and drive characteristics. |
| Package Type | SOIC-14 | SOIC-14 | Package compatibility is required for direct PCB footprint replacement. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Temperature range must cover the application environment for reliable performance. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC74D | 74HC7403D,518 |
|---|---|---|
| Supplier | - | NXP USA Inc. |
| Series | 74HC | 74HC |
| Part Status | Active | Obsolete |
| Memory Size | - | 256 (64 x 4) |
| Function | Set(Preset) and Reset | Asynchronous, Synchronous |
| Data Rate | - | 30MHz |
| Access Time | - | 49ns |
| Voltage - Supply | 2V ~ 6V | 2 V ~ 6 V |
| Current - Supply (Max) | - | 1mA |
| Bus Directional | - | Uni-Directional |
| Expansion Type | - | Depth, Width |
| Programmable Flags Support | - | No |
| Retransmit Capability | - | No |
| FWFT Support | - | No |
| Operating Temperature | -40°C ~ 85°C (TA) | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Type | D-Type | - |
| Output Type | Complementary | - |
| Number of Elements | 2 | - |
| Number of Bits per Element | 1 | - |
| Clock Frequency | 67 MHz | - |
| Max Propagation Delay @ V Max CL | 26ns @ 6V, 50pF | - |
| Trigger Type | Positive Edge | - |
| Current - Output High Low | 5.2mA, 5.2mA | - |
| Current - Quiescent (Iq) | 2 µA | - |
| Input Capacitance | 5 pF | - |
Frequently asked questions
Are the 74HC74D and 74HC7403D,518 the same type of logic device?
No. The 74HC74D is a dual D-type positive-edge-triggered flip-flop with set and reset, while the 74HC7403D,518 is a different 74HC-series logic function. They are not functionally equivalent and cannot be treated as the same device.
What is the primary logic function of the 74HC74D?
The 74HC74D contains two independent D-type flip-flops with individual data, set, reset, and clock inputs, plus complementary Q and Q-bar outputs. It is a standard dual D flip-flop in the 74HC family.
What is the primary logic function of the 74HC7403D,518?
The 74HC7403D,518 is a 74HC-series logic device with a different function from the 74HC74D. Its specific logic function and pinout must be confirmed from the manufacturer datasheet, as it is not a dual D flip-flop.
Can the 74HC74D and 74HC7403D,518 be used interchangeably in a design?
No. Because they implement different logic functions and have different pinouts, they are not pin-to-pin or function-to-function replacements. Substitution requires full validation against the target design and manufacturer documentation.
Do the 74HC74D and 74HC7403D,518 share the same package and pin count?
Both are typically offered in SOIC packages, but the 74HC74D is commonly a 14-pin SOIC device, while the 74HC7403D,518 has a different pin count and pinout. Package compatibility alone does not make them interchangeable.
Are the supply voltage and logic-level specifications the same for both parts?
Both belong to the 74HC logic family and generally operate over a 2 V to 6 V supply range with CMOS-compatible input thresholds. However, exact DC and AC characteristics should be verified from the respective manufacturer datasheets before design use.
Which part should be selected for a dual flip-flop application?
The 74HC74D is the appropriate choice for a dual D-type flip-flop function. The 74HC7403D,518 is not a dual flip-flop and should not be selected for that function.
What is the key difference to check before comparing these two parts?
The most important check is the logic function and pinout. The 74HC74D is a dual D flip-flop, while the 74HC7403D,518 is a different 74HC logic device, so their truth tables, control inputs, and output configurations differ.