Part A
74HC259D
東芝電晶體與存儲
- Lifecycle
- Active
- Stock
- 7207 件
- Package
- SOIC-20
- Series
- 邏輯-鎖存器
Replacement verdict
Not a drop-in replacement
The 74HC259D and 74HC245D,652 are functionally unrelated logic ICs and cannot serve as substitutes for one another. The 74HC259D is an 8-bit addressable latch with decoded outputs, while the 74HC245D,652 is an octal bidirectional bus transceiver with 3-state outputs. Their internal architectures, pin functions, and intended applications differ fundamentally, making direct replacement technically infeasible without complete circuit redesign.
Different logic function
Different output type
Different pin function
Different data direction
Parts at a glance
Part B
74HC245D,652
恩智浦美國股份有限公司。
- Lifecycle
- Active
- Stock
- 4100 件
- Package
- SOIC-20
- Series
- 邏輯-緩衝器、驅動器、接收器、收發器
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC259D | 74HC245D,652 | Why it matters |
|---|---|---|---|
| Logic Function | 8-bit addressable latch | Octal bus transceiver with 3-state outputs | The core function determines whether the device can store/select bits or bidirectionally buffer a bus, so they are not functionally interchangeable. |
| Number of Bits / Channels | 8 (latch outputs) | 8 (transceiver channels) | Both are 8-bit wide, but the bit count alone does not make them substitutes because the internal signal flow differs. |
| Directionality | Unidirectional (latched outputs) | Bidirectional (A-to-B or B-to-A) | Bidirectional capability is essential for bus interfacing, while a latch is used for output holding and addressable storage. |
| Output Type | Standard push-pull (active HIGH/LOW latched outputs) | 3-state (tri-state) outputs | 3-state outputs allow bus sharing and high-impedance disconnection, which the latch does not provide. |
| Control Inputs | Address inputs (A0-A2), Enable (E), Clear (CLR), Data (D) | Direction (DIR), Output Enable (OE) | Different control schemes mean the pinout and control logic are incompatible for direct substitution. |
| Supply Voltage Range | 2.0 V to 6.0 V | 2.0 V to 6.0 V | Both support the same HC-family supply range, so voltage compatibility is not a differentiator. |
| Propagation Delay (typical at 5 V) | Approximately 15 ns | Approximately 8 ns | Timing differences affect maximum operating frequency and setup/hold margins in synchronous systems. |
| Package | SO16 (SOIC-16) | SO20 (SOIC-20) | Different package sizes and pin counts prevent drop-in board replacement without layout changes. |
| Pin Count | 16 | 20 | Pin count mismatch means the devices cannot share the same footprint or socket. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both cover the industrial temperature range, so thermal compatibility is equivalent. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC259D | 74HC245D,652 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | D-Type, Addressable | Transceiver, Non-Inverting |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Output Type | Standard | 3-State |
| Current - Output High Low | 5.2mA, 5.2mA | 7.8mA, 7.8mA |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Circuit | 1:8 | - |
| Independent Circuits | 1 | - |
| Delay Time - Propagation | 22ns | - |
Frequently asked questions
What are the primary functional differences between the 74HC259D and the 74HC245D,652?
The 74HC259D is an 8-bit addressable latch that stores individual bits and provides both latching and demultiplexing functions, while the 74HC245D,652 is an octal bus transceiver designed for bidirectional asynchronous data transfer between two buses. They serve fundamentally different logic functions and are not interchangeable.
Do the 74HC259D and 74HC245D,652 have compatible pinouts?
No. The 74HC259D is a 16-pin device with inputs for address selection, data, latch enable, and clear, plus eight latched outputs. The 74HC245D,652 is a 20-pin device with direction control, output enable, and eight bidirectional data pins arranged as two ports. Their pin counts and pin functions differ, so they cannot be used as drop-in replacements.
Can the 74HC259D and 74HC245D,652 operate from the same supply voltage range?
Yes. Both devices are members of the 74HC logic family and are specified for a supply voltage range of 2.0 V to 6.0 V, with typical operation at 5.0 V. This common supply range allows them to be used in the same logic system, provided their individual input and output characteristics are respected.
What are the typical propagation delays for the 74HC259D and 74HC245D,652?
At a 5.0 V supply and 25 °C, the 74HC259D typically exhibits a propagation delay from data or address inputs to outputs of approximately 20 ns to 30 ns, depending on the specific path. The 74HC245D,652 typically shows a propagation delay of approximately 10 ns to 15 ns for bus-to-bus transfers. These values are typical and should be verified against the latest manufacturer datasheets for worst-case design margins.
Are the 74HC259D and 74HC245D,652 both available in SOIC packages?
Yes. The 74HC259D is commonly offered in a 16-pin SOIC package, and the 74HC245D,652 is commonly offered in a 20-pin SOIC package. The package type is similar, but the pin counts and body widths differ, so PCB land patterns are not compatible.
Which device is suitable for driving a shared data bus, the 74HC259D or the 74HC245D,652?
The 74HC245D,652 is specifically designed for bus-oriented applications because it provides bidirectional non-inverting buffers with three-state outputs and a direction control pin. The 74HC259D provides latched outputs that can be used for demultiplexing or storing control signals, but it is not intended as a bidirectional bus transceiver.
Can the 74HC259D and 74HC245D,652 be used together in the same design?
Yes. Because both are 74HC-family devices with compatible supply voltage and logic-level specifications, they can be used together. For example, the 74HC259D can generate latched control or select signals, while the 74HC245D,652 can handle bidirectional data transfer on a shared bus, provided timing and loading constraints are satisfied.
What are the output drive capabilities of the 74HC259D and 74HC245D,652?
Both devices typically provide standard 74HC output drive of ±4 mA at 5.0 V, which is sufficient for driving CMOS inputs and low-power loads. The 74HC245D,652 is optimized for bus driving with symmetrical source and sink currents, while the 74HC259D outputs are latched and also provide standard 74HC drive. For higher current requirements, external buffers or drivers should be used.