Part A
74HC595D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 4369 Stückzahl
- Package
- SOIC-16
- Series
- Logic-Shift-Register
Replacement verdict
Not a drop-in replacement
The 74HC573D and 74HC595D are not functionally interchangeable despite sharing the same 74HC CMOS logic family and SOIC-16 package. The 74HC573D is an octal D-type transparent latch with 3-state outputs intended for parallel data latching, while the 74HC595D is an 8-bit serial-in/parallel-out shift register with an internal storage register and 3-state outputs intended for serial data expansion. Their internal architectures, pin functions, and control signal sets differ fundamentally, so neither device can directly substitute for the other in an existing design without significant circuit redesign.
Different logic function
Different pin functions
Different data interface
Different control signals
Parts at a glance
Part B
74HC573D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 3424 Stückzahl
- Package
- SOIC-14
- Series
- Logic-Verriegelungen
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC573D | 74HC595D | Why it matters |
|---|---|---|---|
| Logic Function | Octal D-type transparent latch with 3-state outputs | 8-bit serial-in, serial/parallel-out shift register with output latches and 3-state outputs | Defines the core behavior; a latch captures parallel data while a shift register serializes data, so they are not functionally interchangeable. |
| Data Input Type | Parallel (8-bit D inputs) | Serial (DS) with parallel outputs | Determines how data is loaded; parallel loading versus serial shifting changes the required interface and pin count. |
| Number of Outputs | 8 parallel 3-state outputs | 8 parallel 3-state outputs plus serial output QH' | Affects cascading and fan-out capability; the extra serial output allows daisy-chaining multiple devices. |
| Latch/Register Control | Latch Enable (LE) and Output Enable (OE) | Shift Register Clock (SHCP), Storage Register Clock (STCP), Output Enable (OE), and Shift Register Clear (MR) | Control pins dictate timing and data flow; the 595 requires clocked shifting and separate latching, while the 573 uses a simple transparent latch. |
| Propagation Delay (typical at 5 V) | Approximately 14 ns (tPHL/tPLH) | Approximately 15 ns (shift clock to output) | Influences maximum operating frequency and timing margins in high-speed designs. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Determines compatibility with logic levels and power rails in the target system. |
| Output Drive Current | ±6 mA (at 4.5 V) | ±6 mA (at 4.5 V) | Sets the ability to drive loads such as LEDs or other logic inputs directly. |
| Package | SOIC-20 (D suffix) | SOIC-16 (D suffix) | Footprint and pin count affect PCB layout and cannot be swapped without redesign. |
| Pin Count | 20 pins | 16 pins | Different pin counts mean the devices are not drop-in replacements and require different board routing. |
| Primary Application | Data latching, bus holding, and addressable latch applications | GPIO expansion, LED driving, and serial-to-parallel conversion | Highlights the intended use cases; substituting one for the other typically requires significant logic or firmware changes. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC595D | 74HC573D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | Shift Register | D-Type Latch |
| Output Type | Tri-State | Tri-State |
| Number of Elements | 1 | - |
| Number of Bits per Element | 8 | - |
| Function | Serial to Parallel, Serial | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Circuit | - | 8:8 |
| Independent Circuits | - | 1 |
| Delay Time - Propagation | - | 26ns |
| Current - Output High Low | - | 7.8mA, 7.8mA |
Frequently asked questions
What is the primary functional difference between the 74HC573D and the 74HC595D?
The 74HC573D is an octal D-type transparent latch with 3-state outputs, used for temporary data storage and bus driving. The 74HC595D is an 8-bit serial-in, parallel-out shift register with a storage register and 3-state outputs, used for serial-to-parallel data conversion and I/O expansion.
Can the 74HC573D and 74HC595D be used interchangeably in a design?
No. They have different data input architectures (parallel vs. serial) and internal logic functions. The 74HC573D requires parallel data inputs and a latch enable, while the 74HC595D requires serial data input, a shift clock, and a storage register clock. Direct substitution is not possible without redesigning the control and data paths.
Do the 74HC573D and 74HC595D have the same pin count and package type?
Both devices are commonly offered in a 16-pin SOIC package (the "D" suffix in 74HC573D and 74HC595D typically denotes SOIC). However, their pin functions and pinouts differ. The 74HC573D has eight parallel data inputs and eight parallel outputs, while the 74HC595D has serial input, shift clock, latch clock, output enable, and eight parallel outputs.
Which device is better for expanding the number of output pins on a microcontroller?
The 74HC595D is generally preferred for output pin expansion because it uses a serial interface, requiring only three microcontroller pins (data, shift clock, latch clock) to control eight or more outputs in a daisy chain. The 74HC573D requires a parallel data bus and a latch enable, consuming more I/O pins on the controller.
What are the output drive capabilities of the 74HC573D and 74HC595D?
Both devices are 74HC series CMOS logic and typically provide standard CMOS output drive. Verified datasheets from manufacturers such as Nexperia, Texas Instruments, and ON Semiconductor specify symmetrical output drive currents, commonly ±6 mA at 4.5 V and ±7.8 mA at 6 V for both devices, though exact limits should be confirmed on the specific manufacturer datasheet.
Can the 74HC595D be used to drive LEDs directly, and how does this compare to the 74HC573D?
Both devices can sink or source limited current for LED driving, but neither is a high-current driver. The 74HC595D is often used for LED control because its serial interface reduces pin count, while the 74HC573D is used when parallel latching of LED data is required. External transistors or constant-current drivers are recommended when LED currents exceed the logic output ratings.
What is the role of the latch enable (LE) on the 74HC573D compared to the latch clock (RCLK) on the 74HC595D?
On the 74HC573D, the latch enable (LE) controls whether the outputs follow the inputs (transparent mode) or hold the last data (latched mode). On the 74HC595D, the storage register clock (RCLK) transfers data from the internal shift register to the output storage register, allowing the outputs to update simultaneously while new serial data is shifted in.
Are the 74HC573D and 74HC595D compatible with 3.3 V logic systems?
Both devices are 74HC family parts and are typically specified for operation from 2.0 V to 6.0 V. They can interface with 3.3 V logic systems when powered from a 3.3 V supply. However, input voltage thresholds and output levels must be verified against the specific manufacturer datasheet to ensure compatibility with the driving and receiving logic levels.