Part A
74HC540D
Компания Toshiba Semiconductor и Storage
- Lifecycle
- Active
- Stock
- 5312 ПКС
- Package
- SOIC-20
- Series
- Логика - буферы, драйверы, приемники, передатчики
Replacement verdict
Not a drop-in replacement
The 74HC540D and 74HC595D,112 serve fundamentally different logic functions and cannot be used interchangeably in a design. The 74HC540D is an octal inverting buffer with 3-state outputs intended for bus driving and signal buffering, while the 74HC595D,112 is an 8-bit serial-in/parallel-out shift register with output latches designed for serial-to-parallel data conversion. Their pinouts, control interfaces, and functional architectures are incompatible, so substituting one for the other would require a complete circuit redesign rather than a direct replacement.
Different logic function
Different output type
Different control interface
Different pinout
Parts at a glance
Part B
74HC595D,112
Компания Nexperia USA Inc.
- Lifecycle
- Active
- Stock
- 3930 ПКС
- Package
- SOIC-16
- Series
- Логические - сменные регистры
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC540D | 74HC595D,112 | Why it matters |
|---|---|---|---|
| Logic Function | Octal buffer/line driver with 3-state inverting outputs | 8-bit serial-in, serial/parallel-out shift register with output latches | Defines the core function; these devices are not functionally interchangeable as they perform entirely different logic operations. |
| Output Type | 3-state inverting | 3-state non-inverting (parallel outputs) | Output polarity and drive configuration affect signal integrity and whether the device can share a bus. |
| Number of Outputs | 8 | 8 | Both provide 8 outputs, but the 74HC595 outputs are latched register outputs rather than direct buffer outputs. |
| Data Interface | Parallel input, parallel output | Serial input, serial/parallel output | Determines how data is loaded; serial interface reduces pin count but requires clocked data transfer. |
| Latch/Register | None | 8-bit shift register plus 8-bit output latch | Latched outputs allow data to be held stable while new data is shifted in, enabling cascaded operation. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both are HC-family CMOS devices with the same supply range, allowing use in 3.3 V and 5 V systems. |
| Propagation Delay (typical at 5 V) | ~8 ns | ~14 ns (shift clock to output) | Affects maximum operating frequency and timing margins in high-speed designs. |
| Output Drive Current | ±6 mA (at 5 V) | ±6 mA (at 5 V) | Determines fan-out and ability to drive LEDs or other loads directly. |
| Package | SO16 (SOIC-16) | SO16 (SOIC-16) | Same package footprint allows PCB layout compatibility, though pin functions differ. |
| Pin Count | 16 | 16 | Identical pin count but different pin assignments; direct drop-in replacement is not possible. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC540D | 74HC595D,112 |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HC | 74HC |
| Part Status | Active | Obsolete |
| Logic Type | Buffer, Inverting | Shift Register |
| Output Type | 3-State | Tri-State |
| Number of Elements | 1 | 1 |
| Number of Bits per Element | 8 | 8 |
| Function | - | Serial to Parallel, Serial |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C (TA) | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Current - Output High Low | 7.8mA, 7.8mA | - |
Frequently asked questions
What are the primary functional differences between the 74HC540D and the 74HC595D,112?
The 74HC540D is an octal buffer/line driver with 3-state outputs and inverting functionality, designed for driving bus lines or buffer memory address registers. The 74HC595D,112 is an 8-bit serial-in, parallel-out shift register with a storage register and 3-state parallel outputs, used for serial-to-parallel data conversion and LED driving. They serve fundamentally different logic functions and are not interchangeable.
Are the 74HC540D and 74HC595D,112 pin-compatible?
No. The 74HC540D is typically supplied in a 20-pin SOIC package with a pinout optimized for octal buffer functions, including direction control and output enable pins. The 74HC595D,112 is supplied in a 16-pin SOIC package with a pinout for serial data input, shift clock, latch clock, output enable, and serial data output. The package sizes and pin counts differ, so they are not pin-compatible.
Can the 74HC540D be used to drive LEDs in the same way as the 74HC595D,112?
No. The 74HC540D provides parallel inverting buffers with 3-state outputs and does not include a serial interface or internal storage register. The 74HC595D,112 includes an 8-bit shift register, an 8-bit storage register, and parallel 3-state outputs specifically suited for serial-to-parallel conversion and LED driving. Using the 74HC540D for serial LED control would require additional external logic and is not a direct substitute.
What are the key electrical characteristics of the 74HC540D?
The 74HC540D operates over a wide supply voltage range of 2.0 V to 6.0 V, features inverting 3-state outputs, and provides high noise immunity consistent with CMOS technology. It is specified for balanced propagation delays and can drive up to 15 LSTTL loads. Exact current drive and timing parameters should be verified from the manufacturer datasheet.
What are the key electrical characteristics of the 74HC595D,112?
The 74HC595D,112 operates over a supply voltage range of 2.0 V to 6.0 V, includes an 8-bit serial-in/parallel-out shift register with a storage register, and provides 3-state parallel outputs. It supports serial cascading via a serial data output pin and is specified for balanced propagation delays and high noise immunity. Exact drive current and timing parameters should be verified from the manufacturer datasheet.
Do both devices support 3-state outputs?
Yes. Both the 74HC540D and the 74HC595D,112 feature 3-state outputs, allowing their outputs to be placed in a high-impedance state for bus sharing or multiplexing. However, the control mechanisms differ: the 74HC540D uses output enable pins for the octal buffer, while the 74HC595D,112 uses an output enable pin for the parallel storage register outputs.
Which device is more suitable for expanding microcontroller I/O?
The 74HC595D,112 is generally more suitable for expanding microcontroller I/O because it converts serial data from a few microcontroller pins into 8 parallel outputs and supports cascading for additional outputs. The 74HC540D is a buffer/driver and does not provide serial-to-parallel conversion, so it is used for signal buffering or driving rather than I/O expansion.
Are the 74HC540D and 74HC595D,112 interchangeable in existing designs?
No. They differ in logic function, pin count, package size, and control interface. The 74HC540D is an inverting octal buffer with 3-state outputs, while the 74HC595D,112 is a serial-in/parallel-out shift register with storage and 3-state outputs. Direct substitution is not possible without redesigning the circuit and validating all timing, drive, and control requirements against the respective manufacturer datasheets.