Part A
74HC574D
東芝電晶體與存儲
- Lifecycle
- Active
- Stock
- 3287 件
- Package
- SOIC-20
- Series
- 邏輯-觸發器
Replacement verdict
Not a drop-in replacement
The 74HC574D and 74HC595D,118 are not functionally interchangeable despite sharing the same 74HC CMOS logic family and SO-16 package. The 74HC574D is an octal D-type flip-flop with 3-state outputs intended for parallel data storage and bus interfacing, while the 74HC595D,118 is an 8-bit serial-in/parallel-out shift register with an integrated output latch and 3-state outputs intended for serial-to-parallel data conversion and I/O 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 circuit and firmware modification.
Different logic function
Different data interface
Different pinout
Different control signals
Parts at a glance
Part B
74HC595D,118
恩智浦美國股份有限公司。
- Lifecycle
- Active
- Stock
- 2450 件
- Package
- SOIC-16
- Series
- 邏輯-位移暫存器
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC574D | 74HC595D,118 | Why it matters |
|---|---|---|---|
| Logic Function | Octal D-type flip-flop with 3-state outputs | 8-bit serial-in, serial/parallel-out shift register with output latches | Defines the core operation; these devices are not functionally interchangeable as they perform different logic functions. |
| Output Type | 3-state (tri-state) parallel outputs | 3-state serial/parallel outputs with separate storage register | Determines how outputs can be driven and shared on a bus; affects interface design. |
| Data Input Interface | Parallel D inputs (8-bit) | Serial input (with serial data and shift clock) | Dictates the host interface; parallel loading versus serial shifting requires different control signals and wiring. |
| Number of Pins | 20 | 16 | Pin count affects PCB footprint and package compatibility; they are not drop-in replacements. |
| Package | SO20 (20-pin small outline) | SO16 (16-pin small outline) | Different package sizes mean different land patterns; cannot be substituted without board redesign. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both support the same HC-family supply range, so voltage compatibility is not a differentiator. |
| Output Current (per pin) | ±4 mA (typical at 4.5 V) | ±4 mA (typical at 4.5 V) | Similar drive strength means neither offers an advantage for driving heavier loads. |
| Propagation Delay | Approximately 15 ns at 4.5 V | Approximately 15 ns at 4.5 V | Comparable speed; timing is not a deciding factor for substitutability. |
| Latch/Register | Single register (D flip-flop) | Shift register plus separate output storage register | The 595 allows data to be shifted without disturbing outputs, while the 574 updates outputs directly on clock edge. |
| Typical Applications | Bus interfacing, data storage, address latching | LED drivers, I/O expansion, serial-to-parallel conversion | Different intended uses reflect their non-interchangeable roles in a design. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC574D | 74HC595D,118 |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | - | Shift Register |
| Output Type | Tri-State, Non-Inverted | Tri-State |
| Number of Elements | 1 | 1 |
| Number of Bits per Element | 8 | 8 |
| Function | Standard | 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 |
| Type | D-Type | - |
| Clock Frequency | 59 MHz | - |
| Max Propagation Delay @ V Max CL | 33ns @ 6V, 150pF | - |
| Trigger Type | Positive Edge | - |
| Current - Output High Low | 7.8mA, 7.8mA | - |
| Current - Quiescent (Iq) | 4 µA | - |
| Input Capacitance | 5 pF | - |
Frequently asked questions
What are the primary functional differences between the 74HC574D and the 74HC595D,118?
The 74HC574D is an octal D-type flip-flop with 3-state outputs, used for parallel data storage and buffering. The 74HC595D,118 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.
Are the 74HC574D and 74HC595D,118 pin-compatible?
No. The 74HC574D is typically supplied in a 20-pin SOIC package with a pinout optimized for parallel D-type inputs and 3-state outputs. The 74HC595D,118 is typically supplied in a 16-pin SOIC package with pins for serial input, shift clock, storage clock, output enable, and serial output. They are not pin-compatible.
Can the 74HC574D and 74HC595D,118 be used together in the same design?
Yes. They serve different functions and can be used together. For example, a 74HC595D,118 can convert serial data to parallel, and a 74HC574D can latch and buffer that parallel data for driving loads or a bus.
What are the key operating voltage and logic family specifications for both devices?
Both are 74HC series high-speed CMOS devices. They typically operate over a supply voltage range of 2.0 V to 6.0 V, with standard CMOS input thresholds and 3-state outputs. Exact limits should be confirmed from the respective manufacturer datasheets.
Which device is better for expanding the number of output pins on a microcontroller?
The 74HC595D,118 is generally better for output pin expansion because it requires only three control lines (serial data, shift clock, storage clock) to drive eight outputs and can be cascaded. The 74HC574D requires eight parallel data lines plus a clock and output enable, consuming more microcontroller pins.
Do both devices have 3-state outputs?
Yes. Both the 74HC574D and the 74HC595D,118 feature 3-state outputs, allowing their outputs to be placed in a high-impedance state for bus sharing or disabling connected loads.
What is the difference in data loading between the 74HC574D and the 74HC595D,118?
The 74HC574D loads all eight bits in parallel on a single clock edge. The 74HC595D,118 loads data serially, one bit per shift clock edge, into an internal shift register, then transfers the byte to a storage register on a separate latch clock edge.
Are the 74HC574D and 74HC595D,118 directly interchangeable in an existing PCB design?
No. They differ in package pin count, pinout, and internal logic function. Direct substitution without PCB redesign and firmware changes is not possible.