Part A
74HC594D
Компания Toshiba Semiconductor и Storage
- Lifecycle
- Active
- Stock
- 1976 ПКС
- Package
- SOIC-16
- Series
- Логические - сменные регистры
Replacement verdict
Not a drop-in replacement
The 74HC573D and 74HC594D are not functionally interchangeable despite sharing the same 74HC CMOS logic family and SO16 package. The 74HC573D is an octal transparent D-type latch with 3-state outputs intended for bus-holding and address latching, while the 74HC594D is an 8-bit serial-in/parallel-out shift register with an internal storage register and no 3-state capability. Their input topology, output behavior, and control signal sets differ fundamentally, so substituting one for the other requires a complete redesign of the surrounding interface logic rather than a direct drop-in replacement.
Different logic function
Different output type
Different input interface
Different control signals
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 | 74HC594D | Why it matters |
|---|---|---|---|
| Logic Function | Octal D-type transparent latch with 3-state outputs | 8-bit serial-in/parallel-out shift register with output latches | The core function differs fundamentally: one latches parallel data, the other shifts serial data, so they are not functionally interchangeable. |
| Data Input Type | Parallel (8-bit D inputs) | Serial (DS input) with shift register | Input interface determines how data is loaded into the device and affects system architecture. |
| Output Type | 3-state parallel outputs | Parallel outputs (non-3-state, from output register) | 3-state outputs allow bus sharing; the absence of 3-state on the 74HC594D limits direct bus connection. |
| Number of Outputs | 8 | 8 | Both provide 8 outputs, but they are driven by different internal registers. |
| Latch/Register Stages | Single transparent latch stage | Shift register plus separate output latch register | The 74HC594D allows serial shifting without disturbing outputs until latched, enabling different timing behavior. |
| Control Inputs | LE (latch enable), OE (output enable) | SHCP (shift clock), STCP (storage/latch clock), MR (master reset), OE (output enable) | Different control pin sets mean incompatible pinouts and control logic. |
| Serial Output | None | Q7' serial output for cascading | Cascading capability of the 74HC594D enables expansion; the 74HC573D cannot be cascaded in the same way. |
| Package | SO16 (D suffix) | SO16 (D suffix) | Same package footprint, but pin functions differ, so direct drop-in replacement is not possible. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both operate over the standard HC family voltage range, so supply compatibility is not a differentiator. |
| Propagation Delay (typical at 4.5 V) | Approximately 14 ns (LE to Q) | Approximately 15 ns (SHCP to Q7') | Similar speed class, but timing paths differ due to different internal architectures. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC594D | 74HC573D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | Shift Register | D-Type Latch |
| Output Type | Push-Pull | 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 74HC594D?
The 74HC573D is an octal D-type transparent latch with 3-state outputs, designed for temporary data storage and bus driving. The 74HC594D is an 8-bit serial-in/parallel-out shift register with an output register, designed for serial-to-parallel data conversion. They serve fundamentally different logic functions and are not pin-to-pin or function-to-function replacements.
Are the 74HC573D and 74HC594D pin-compatible?
No. Both devices are typically offered in a 16-pin SOIC package (the "D" suffix), but their pinouts differ. The 74HC573D has 8 data inputs, 8 data outputs, a latch enable (LE), and an output enable (OE). The 74HC594D has a serial data input, a shift clock, a storage/latch clock, a reset, and 8 parallel outputs. Pin functions and assignments are not interchangeable.
Can the 74HC573D and 74HC594D be used together in the same design?
Yes. They are often used together in embedded systems. For example, a 74HC594D can convert a microcontroller's serial data stream into parallel outputs, while a 74HC573D can latch and drive a separate parallel bus. Their different functions make them complementary rather than competing devices.
What are the key operating voltage and logic family specifications for both devices?
Both are members of the 74HC high-speed CMOS logic family. They typically operate over a supply voltage range of 2.0 V to 6.0 V, with standard CMOS input thresholds and low power consumption. Exact limits, propagation delays, and drive currents should be verified from the respective manufacturer datasheets (e.g., Nexperia, Texas Instruments, or ON Semiconductor).
Which device is better for expanding the number of parallel outputs from a microcontroller?
The 74HC594D is generally better for output expansion because it accepts serial data and provides 8 parallel outputs, requiring only a few microcontroller pins. The 74HC573D requires 8 parallel data lines plus control signals, making it less efficient for simple output expansion but suitable for latching an existing parallel bus.
Do both devices have 3-state outputs?
No. The 74HC573D has 3-state outputs controlled by the output enable (OE) pin, allowing the outputs to be placed in a high-impedance state for bus sharing. The 74HC594D has standard push-pull parallel outputs and does not provide a 3-state output mode.
What is the role of the storage register in the 74HC594D compared to the latch in the 74HC573D?
In the 74HC594D, the storage register holds the parallel output data stable while new serial data is shifted into the internal shift register, preventing output glitches during serial loading. In the 74HC573D, the latch is transparent when LE is high and holds the last data when LE goes low; there is no separate shift register stage.
Are the 74HC573D and 74HC594D available in identical package options?
Both are commonly available in 16-pin SOIC (D suffix), as well as other packages such as TSSOP or DIP depending on the manufacturer. However, package availability can vary by supplier and should be confirmed using distributor listings or official datasheets. Package compatibility alone does not imply functional equivalence.