Part A
74HC594D
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 1976 PCS
- Package
- SOIC-16
- Series
- Logic - Shift Registers
Replacement verdict
Compatible functional replacement candidate
The 74HC594D and 74HC595D,112 are functionally compatible 8-bit serial-in/parallel-out shift registers with output latches, sharing identical logic function, package footprint, and supply voltage range. The primary distinction is the 74HC594D's direct parallel data inputs for register loading versus the 74HC595D's serial-only data entry, which may affect system architecture but does not preclude functional substitution in most shift-register applications.
Logic Function
High match
Package Type
High match
Supply Voltage Range
High match
Data Input Configuration
Validation required
Parts at a glance
Part B
74HC595D,112
Nexperia Hoa Kỳ Inc.
- Lifecycle
- Active
- Stock
- 3930 PCS
- Package
- SOIC-16
- Series
- Logic - Shift Registers
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 | 74HC595D,112 | Why it matters |
|---|---|---|---|
| Function | 8-bit serial-in/serial or parallel-out shift register with output register | 8-bit serial-in/serial or parallel-out shift register with output latches (3-state) | Defines the core logic behavior; the 74HC594 has a direct parallel output register while the 74HC595 has 3-state output latches, affecting bus sharing and drive capability. |
| Output Type | Parallel outputs (non-3-state) | 3-state parallel outputs | 3-state outputs allow multiple devices to share a common bus, while non-3-state outputs cannot be disabled, limiting bus multiplexing. |
| Number of Pins | 16 | 16 | Pin count determines package footprint and PCB layout compatibility; both are 16-pin devices but pin functions differ. |
| Output Enable Control | No output enable (OE) pin | Yes, active-low OE pin | The OE pin on the 74HC595 allows outputs to be placed in high-impedance state, enabling bus sharing and power-saving modes not possible with the 74HC594. |
| Latch/Register Clock | Separate storage register clock (RCLK) | Separate storage register clock (RCLK) | Both devices use a separate latch clock to transfer shift register data to outputs, allowing stable output updates without disturbing the shift process. |
| Shift Register Clear | Asynchronous clear (active-low SRCLR) | Asynchronous clear (active-low SRCLR) | The clear pin resets the shift register to zero, which is essential for initialization and error recovery in serial data chains. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Determines compatibility with logic families and power supplies; both support standard HC-family voltage levels. |
| Output Drive Current | ±4 mA (typical at 5 V) | ±6 mA (typical at 5 V) | Drive current affects the ability to directly drive LEDs, relays, or other loads; the 74HC595 offers slightly higher output current. |
| Propagation Delay | ~15 ns (typical at 5 V) | ~15 ns (typical at 5 V) | Propagation delay impacts maximum serial clock frequency and timing margins in high-speed shift register applications. |
| Package Type | SO16 (SOIC-16) | SO16 (SOIC-16) | Package type determines PCB footprint and thermal characteristics; both use the same SO16 package for drop-in compatibility. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC594D | 74HC595D,112 |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HC | 74HC |
| Part Status | Active | Obsolete |
| Logic Type | Shift Register | Shift Register |
| Output Type | Push-Pull | Tri-State |
| Number of Elements | 1 | 1 |
| Number of Bits per Element | 8 | 8 |
| Function | Serial to Parallel, Serial | Serial to Parallel, Serial |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What is the main functional difference between the 74HC594D and the 74HC595D,112?
The 74HC594D is an 8-bit serial-in/serial or parallel-out shift register with an output register, while the 74HC595D,112 is an 8-bit serial-in/serial or parallel-out shift register with an output register and a 3-state output stage. The 74HC595D,112 provides a serial data output (Q7') for cascading and a 3-state enable (OE) for the parallel outputs, whereas the 74HC594D does not have a 3-state output enable; its parallel outputs are always active.
Are the 74HC594D and 74HC595D,112 pin-compatible?
No, they are not pin-compatible. The 74HC594D has a 16-pin SO package with a different pinout: it lacks the 3-state output enable (OE) and the serial data output (Q7') found on the 74HC595D,112. The 74HC595D,112 also uses a 16-pin SO package but assigns pins for OE and Q7', which are not present on the 74HC594D.
Can the 74HC595D,112 be used as a direct replacement for the 74HC594D?
No, a direct replacement is not possible without design changes. The 74HC595D,112 has additional pins (OE and Q7') and a 3-state output feature that the 74HC594D does not have. The PCB footprint and pin functions differ, so substituting one for the other requires verifying the schematic and layout against the respective manufacturer datasheets.
What is the function of the output register in both the 74HC594D and 74HC595D,112?
In both devices, the output register stores the shifted data and transfers it to the parallel outputs on the rising edge of the storage register clock (STCP). This allows the shift register to continue shifting new data while the parallel outputs remain stable, preventing output glitches during serial loading.
Do both the 74HC594D and 74HC595D,112 support cascading for wider parallel output?
Only the 74HC595D,112 supports cascading directly through its serial data output (Q7'). The 74HC594D does not provide a serial data output pin, so cascading multiple 74HC594D devices for wider parallel output is not possible without external logic.
What are the supply voltage and logic family specifications for the 74HC594D and 74HC595D,112?
Both devices are part 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 74HC input and output characteristics. For exact limits and timing parameters, refer to the respective manufacturer datasheets from Nexperia or Texas Instruments.
Which device is better for applications requiring output disabling or bus sharing?
The 74HC595D,112 is better suited for bus sharing or output disabling because it includes a 3-state output enable (OE) pin. When OE is high, the parallel outputs are placed in a high-impedance state, allowing other devices to drive the same bus. The 74HC594D lacks this feature, so its outputs cannot be disabled.