Part A
74HC595D
Toshiba Semiconductor and Storage
- Lifecycle
- Active
- Stock
- 4369 PCS
- Package
- SOIC-16
- Series
- Lógica - Registos de Maiúsculas
Replacement verdict
Not a drop-in replacement
The 74HC540D and 74HC595D are functionally unrelated devices and cannot be used as substitutes for one another. The 74HC540D is an inverting octal buffer/line driver with 3-state outputs, while the 74HC595D is an 8-bit serial-in/parallel-out shift register with output latches. Their logic functions, pinouts, and control interfaces differ fundamentally, so replacing one with the other is not feasible in any design.
Different logic function
Different output type
Different pinout
Different control interface
Parts at a glance
Part B
74HC540D
Toshiba Semiconductor and Storage
- Lifecycle
- Active
- Stock
- 5312 PCS
- Package
- SOIC-20
- Series
- Lógica - Buffers, Drivers, Receivers, Transceivers
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 | Why it matters |
|---|---|---|---|
| Logic Function | Octal inverting buffer/line driver with 3-state outputs | 8-bit serial-in, serial/parallel-out shift register with output latches and 3-state outputs | Defines the core function; these devices are not functionally interchangeable as they perform entirely different logic operations. |
| Number of Bits / Channels | 8 buffers (octal) | 8-bit shift register | Both handle 8 signals, but the internal data path differs (parallel buffer vs. serial shift), affecting how data is loaded and transferred. |
| Output Type | 3-state inverting | 3-state non-inverting (with latched outputs) | Inverting vs. non-inverting outputs changes signal polarity, and the 595's latches allow data to be held while new data is shifted in. |
| Data Input Interface | Parallel (8 inputs) | Serial (DS input) with shift clock | Determines how data is presented to the device; parallel loading is faster per byte, while serial loading reduces pin count. |
| Control Inputs | OE1, OE2 (output enable, active low) | SHCP, STCP, MR, OE | Different control schemes dictate timing and system design; the 595 requires shift and storage clocks plus master reset. |
| Propagation Delay (typical at 4.5V) | ~13 ns | ~20 ns (shift clock to output) | Affects maximum operating frequency and timing margins in high-speed designs. |
| Output Drive Current (per pin) | ±6 mA (at 4.5V) | ±6 mA (at 4.5V) | Determines fan-out and ability to drive loads; both have similar drive strength in the HC family. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both are compatible with common 3.3V and 5V logic systems, allowing similar power supply design. |
| Package | SO16 (D package) | SO16 (D package) | Same footprint allows PCB layout compatibility, but pin functions differ so they are not drop-in replacements. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +125°C | Both suitable for industrial temperature environments, ensuring similar reliability across applications. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC595D | 74HC540D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | Shift Register | Buffer, Inverting |
| Output Type | Tri-State | 3-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 ~ 125°C | -40°C ~ 85°C (TA) |
| 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?
The 74HC540D is an octal buffer/line driver with 3-state outputs and inverting functionality, designed for driving bus lines or buffering signals. The 74HC595D is an 8-bit serial-in, parallel-out shift register with a storage register and 3-state output registers, used for serial-to-parallel data conversion and I/O expansion.
Can the 74HC540D and 74HC595D be used interchangeably in a circuit design?
No, they are not interchangeable. The 74HC540D provides parallel buffering/inversion with 3-state control, while the 74HC595D performs serial-to-parallel conversion with latching. Their pinouts, functions, and control logic differ fundamentally, so direct substitution is not possible without redesign.
What are the package and pin count specifications for the 74HC540D and 74HC595D?
Both devices are typically offered in a 16-pin SOIC package (the "D" suffix in NXP/Philips naming denotes SOIC). The 74HC540D has 16 pins for octal buffer functions, and the 74HC595D also has 16 pins for shift register functions, but the pin assignments are different between the two.
What are the supply voltage and logic level characteristics of the 74HC540D and 74HC595D?
Both are 74HC series CMOS devices, operating from 2.0 V to 6.0 V supply voltage, with typical 5 V operation. They feature standard CMOS logic thresholds and low power consumption, and their inputs are compatible with LSTTL outputs when VCC is 4.5 V to 5.5 V.
How do the output drive capabilities compare between the 74HC540D and 74HC595D?
Both devices provide standard 74HC output drive: typically ±4 mA at 5 V for balanced drive, with some manufacturers specifying up to ±6 mA. The 74HC540D is specifically characterized for bus driving with 3-state outputs, while the 74HC595D outputs are also 3-state but intended for parallel load driving rather than high-speed bus buffering.
What control signals are required to operate the 74HC540D versus the 74HC595D?
The 74HC540D uses two active-low output enable inputs (OE1 and OE2) to control the 3-state outputs, and all eight inputs are directly transferred to outputs with inversion. The 74HC595D requires a serial data input (DS), a shift clock (SHCP), a storage latch clock (STCP), an output enable (OE), and a serial clear (MR) to manage shifting, latching, and output enabling.
Are the 74HC540D and 74HC595D available in identical temperature and qualification grades?
Both are commonly available in industrial temperature range (-40 °C to +85 °C) and sometimes extended range (-40 °C to +125 °C) depending on manufacturer. Automotive-qualified versions may exist for both, but specific qualification must be verified per manufacturer datasheet and part number suffix.
Which applications are best suited for the 74HC540D compared to the 74HC595D?
The 74HC540D is ideal for bus buffering, signal inversion, and driving high-capacitance loads in microprocessor systems. The 74HC595D is suited for LED matrix control, port expansion, and serial data transmission to parallel outputs, where latching and shift register functionality are required.