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 74HC245D and 74HC259D are functionally unrelated logic ICs and cannot serve as substitutes for one another. The 74HC245D is an octal bidirectional bus transceiver designed for signal buffering and direction-controlled data transfer, while the 74HC259D is an 8-bit addressable latch intended for data storage and demultiplexing. Their internal architectures, pin functions, and control logic differ fundamentally, making direct replacement impossible without complete circuit redesign.
Different logic function
Different pin function
Different control interface
Different data flow direction
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC245D | 74HC259D | Why it matters |
|---|---|---|---|
| Logic Function | Octal bus transceiver with 3-state outputs | 8-bit addressable latch | The core function determines whether the devices can substitute each other; a transceiver and an addressable latch perform fundamentally different logic operations. |
| Number of Bits / Channels | 8 (bidirectional) | 8 (latch outputs) | Both handle 8 bits, but the direction and control of data flow differ, affecting system architecture compatibility. |
| Output Type | 3-state (tri-state) outputs | Standard totem-pole (non-3-state) outputs | 3-state outputs allow bus sharing and high-impedance disconnection, which the latch cannot provide, limiting direct bus interfacing. |
| Direction Control | Direction pin (DIR) selects A-to-B or B-to-A | No direction control; data flows from input to latched output | Bidirectional capability is essential for bus transceiver applications, while the latch is unidirectional. |
| Latch / Storage Element | None (combinational buffer) | 8 addressable D-type latches | The presence of latches enables data storage and addressable output selection, which the transceiver lacks. |
| Address Inputs | None | 3 address inputs (A0, A1, A2) for selecting one of 8 latches | Address inputs allow individual latch selection, a feature absent in the transceiver, affecting control complexity. |
| Enable / Control Pins | Output Enable (OE) and Direction (DIR) | Enable (E) and Latch Enable (LE) or similar | Different control schemes mean the devices cannot be swapped without redesigning the control logic. |
| Propagation Delay (typical at 5V) | ~12 ns (tPD) | ~20 ns (tPD) | Timing differences can affect setup/hold margins and maximum operating frequency in synchronous systems. |
| Package | SOIC-20 (D suffix) | SOIC-16 (D suffix) | Different pin counts and footprints prevent direct PCB drop-in replacement without layout changes. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Identical supply voltage compatibility allows both to operate in the same logic-level systems. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC259D | 74HC245D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | D-Type, Addressable | Transceiver, Non-Inverting |
| Circuit | 1:8 | - |
| Output Type | Standard | 3-State |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Independent Circuits | 1 | - |
| Delay Time - Propagation | 22ns | - |
| Current - Output High Low | 5.2mA, 5.2mA | 7.8mA, 7.8mA |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
Frequently asked questions
What are the primary functions of the 74HC245D and 74HC259D?
The 74HC245D is an octal bus transceiver with 3-state outputs, designed for bidirectional asynchronous communication between data buses. The 74HC259D is an 8-bit addressable latch that stores individual bits and provides both latching and demultiplexing functions.
Can the 74HC245D and 74HC259D be used interchangeably in a circuit?
No. The 74HC245D is a bus transceiver for bidirectional data transfer, while the 74HC259D is an addressable latch for storing and decoding data. Their pin functions, logic operations, and control signals are fundamentally different, so they are not pin-compatible or functionally interchangeable.
What are the key differences in pin configuration between the 74HC245D and 74HC259D?
The 74HC245D has 20 pins in a SOIC package, including direction control (DIR), output enable (OE), and eight bidirectional data pins (A0–A7, B0–B7). The 74HC259D has 16 pins in a SOIC package, featuring eight latch outputs (Q0–Q7), three address inputs (A0–A2), a data input (D), a latch enable (LE), and a clear input (CLR).
What are the typical operating voltage and logic family specifications for both devices?
Both the 74HC245D and 74HC259D 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.
How do the output drive capabilities compare between the 74HC245D and 74HC259D?
Both devices provide standard 74HC output drive, typically ±4 mA at 5 V supply. However, the 74HC245D features 3-state outputs that can be placed in high-impedance mode, while the 74HC259D provides active-high latched outputs without 3-state capability.
What are the typical applications for the 74HC245D and 74HC259D?
The 74HC245D is commonly used for bus interfacing, data buffering, and bidirectional level shifting in microprocessor systems. The 74HC259D is used for addressable latching, LED display driving, relay control, and demultiplexing applications where individual bits must be stored and controlled.
Do the 74HC245D and 74HC259D have the same package and pin count?
No. The 74HC245D is typically supplied in a 20-pin SOIC package, while the 74HC259D is typically supplied in a 16-pin SOIC package. They are not footprint-compatible.
What control signals are available on each device?
The 74HC245D provides an output enable (OE) and a direction control (DIR) pin. The 74HC259D provides a latch enable (LE), a clear (CLR) input, and three address inputs (A0–A2) for selecting which latch output is updated.