Part A
74HC594D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 1976 PCS
- Package
- SOIC-16
- Series
- Logique - Registre à décalage
Replacement verdict
Not a drop-in replacement
The 74HC594D and 74HC540D,652 are functionally unrelated devices and cannot serve as substitutes for one another. The 74HC594D is an 8-bit serial-in/parallel-out shift register with output latches, while the 74HC540D,652 is an octal inverting 3-state buffer/line driver. Their logic functions, pinouts, and I/O architectures differ fundamentally, so neither part can directly replace the other in an existing design.
Different logic function
Different output type
Different pinout
Different input architecture
Parts at a glance
Part B
74HC540D,652
NXP USA Inc.
- Lifecycle
- Active
- Stock
- 2550 PCS
- Package
- SOIC-20
- Series
- Logique - Buffers, lecteurs, récepteurs, émetteurs - récepteurs
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC594D | 74HC540D,652 | Why it matters |
|---|---|---|---|
| Logic Function | 8-bit serial-in/parallel-out shift register with output latches | Octal inverting buffer/line driver with 3-state outputs | The core logic function determines whether the devices are functionally interchangeable; these two parts perform entirely different operations. |
| Output Type | Parallel register outputs (push-pull) | 3-state inverting outputs | Output configuration affects bus interfacing capability and whether outputs can be shared on a common data bus. |
| Number of Outputs | 8 parallel outputs | 8 inverting outputs | Output count must match the application's channel requirements for direct substitution. |
| Input Type | Serial data input with shift register clock and latch clock | Parallel data inputs with output enable | Input architecture determines the data loading method and required control signals. |
| Output Enable Control | No output enable; outputs always active | Dual output enable pins (active low) | Output enable allows high-impedance state for bus sharing, which is essential in multiplexed systems. |
| Signal Inversion | Non-inverting outputs | Inverting outputs | Inversion affects logic polarity and whether signal conditioning matches the surrounding circuitry. |
| Propagation Delay (typical at 5V) | Approximately 15 ns (shift clock to output) | Approximately 8 ns (input to output) | Timing differences can affect setup/hold margins and maximum operating frequency in synchronous designs. |
| Package | SO16 (SOIC-16) | SO20 (SOIC-20) | Package footprint and pin count must match for PCB layout compatibility. |
| Pin Count | 16 pins | 20 pins | Different pin counts mean the devices are not drop-in replacements on the same footprint. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both operate over the standard HC-family supply range, so voltage compatibility is not a differentiator. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC594D | 74HC540D,652 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | Shift Register | Buffer, Inverting |
| Number of Elements | 1 | 1 |
| Number of Bits per Element | 8 | 8 |
| Output Type | Push-Pull | 3-State |
| Current - Output High Low | - | 7.8mA, 7.8mA |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Function | Serial to Parallel, Serial | - |
Frequently asked questions
What are the primary functional differences between the 74HC594D and the 74HC540D,652?
The 74HC594D is an 8-bit serial-in/parallel-out shift register with an 8-bit output latch, while the 74HC540D,652 is an 8-bit inverting octal buffer/line driver with 3-state outputs. The 74HC594D is used for serial-to-parallel data conversion, whereas the 74HC540D,652 is used for bus driving and signal buffering with inverted outputs.
Are the 74HC594D and 74HC540D,652 pin-compatible?
No. The 74HC594D is typically supplied in a 16-pin SOIC package, while the 74HC540D,652 is supplied in a 20-pin SOIC package. They have different pin counts and pin functions, so they are not pin-compatible.
Can the 74HC594D directly replace the 74HC540D,652 in a design?
No. The two devices have different logic functions, pinouts, and package sizes. The 74HC594D cannot directly replace the 74HC540D,652 without significant redesign of the circuit and PCB layout.
What are the output drive capabilities of the 74HC594D and 74HC540D,652?
Both devices are part of the 74HC family and typically provide standard CMOS output drive. The 74HC540D,652 is specified with symmetrical output drive and 3-state outputs, while the 74HC594D provides standard push-pull outputs. For exact drive current ratings, refer to the respective manufacturer datasheets.
Do both devices operate at the same supply voltage range?
Yes. Both the 74HC594D and 74HC540D,652 are 74HC series devices and typically operate over a supply voltage range of 2.0 V to 6.0 V. Always verify the specific operating conditions in the manufacturer datasheet.
Which device is suitable for serial data input and parallel output applications?
The 74HC594D is the appropriate choice for serial-in/parallel-out applications because it contains an 8-bit shift register and an 8-bit output latch. The 74HC540D,652 does not have serial-to-parallel conversion capability.
Which device is suitable for driving a shared bus with high-impedance states?
The 74HC540D,652 is suitable for bus-driving applications because it features 3-state outputs that can be placed in a high-impedance state. The 74HC594D does not have 3-state outputs.
Are the 74HC594D and 74HC540D,652 available in the same package types?
No. The 74HC594D is commonly available in 16-pin packages such as SOIC-16, while the 74HC540D,652 is commonly available in 20-pin packages such as SOIC-20. Package options may vary by manufacturer, so consult the specific datasheet for available package variants.