Part A
74HC126D
東芝セミコンダクター・アンド・ストレージ
- Lifecycle
- Active
- Stock
- 7257 個数
- Package
- SOIC-14
- Series
- ロジック - バッファ、ドライバ、レシーバ、トランシーバ
Replacement verdict
Not a drop-in replacement
The 74HC126D and 74HC165D,653 are not functionally interchangeable. The 74HC126D is a quad bus buffer with 3-state outputs, while the 74HC165D,653 is an 8-bit parallel-in/serial-out shift register. Their logic functions, pin configurations, and signal flow directions are fundamentally different, making direct substitution impossible without complete circuit redesign.
Different logic function
Different output type
Different pin configuration
Different signal direction
Parts at a glance
Part B
74HC165D,653
ネクスペリアUSA株式会社
- Lifecycle
- Active
- Stock
- 9205 個数
- Series
- ロジック - シフトレジスタ
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC126D | 74HC165D,653 | Why it matters |
|---|---|---|---|
| Logic Function | Quad buffer/line driver with 3-state outputs | 8-bit parallel-in/serial-out shift register | The core logic function determines whether the devices are functionally interchangeable; these two parts perform entirely different operations. |
| Number of Channels / Bits | 4 channels | 8 bits | Channel/bit count affects how many signals can be handled simultaneously, impacting circuit design and board layout. |
| Output Type | 3-state (tri-state) outputs | Serial output (with complementary serial output) | Output configuration determines bus interfacing capability and whether multiple devices can share a common data line. |
| Control Inputs | Output enable (OE) per channel | Shift/Load (SH/LD), Clock (CP), Clock Inhibit (CE) | Control pin functions dictate how the device is operated and sequenced within a system. |
| Data Direction | Unidirectional buffering | Parallel input to serial output conversion | Data flow direction is fundamental to whether the part can serve a given signal-routing or data-conversion role. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Matching supply voltage ranges ensures both devices can operate in the same logic-level environment. |
| Logic Family | HC (High-speed CMOS) | HC (High-speed CMOS) | Same logic family ensures compatible input thresholds, output drive, and noise margins. |
| Package | SO14 (SOIC-14) | SO16 (SOIC-16) | Package footprint and pin count must match the PCB layout for physical compatibility. |
| Pin Count | 14 pins | 16 pins | Different pin counts mean the devices are not drop-in replacements and require different PCB footprints. |
| Propagation Delay (typical) | ~11 ns at 4.5 V | ~14 ns at 4.5 V | Propagation delay affects timing margins and maximum operating frequency in synchronous systems. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC126D | 74HC165D,653 |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | Buffer, Non-Inverting | Shift Register |
| Output Type | 3-State | Complementary |
| Number of Elements | 4 | 1 |
| Number of Bits per Element | 1 | 8 |
| Function | - | Parallel or Serial to Serial |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C (TA) | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Base Product Number | - | 74HC165 |
| Current - Output High Low | 7.8mA, 7.8mA | - |
Frequently asked questions
What are the primary functional differences between the 74HC126D and the 74HC165D,653?
The 74HC126D is a quad non-inverting 3-state buffer/line driver with active-HIGH output enable pins, while the 74HC165D,653 is an 8-bit parallel-in/serial-out shift register with a complementary serial output and a serial input for cascading. They serve fundamentally different logic functions and are not interchangeable.
Are the 74HC126D and 74HC165D,653 pin-compatible?
No. The 74HC126D is typically supplied in a 14-pin SOIC package, whereas the 74HC165D,653 is supplied in a 16-pin SOIC package. Pin counts, pin assignments, and functions differ, so they cannot be used as drop-in replacements for each other.
Can the 74HC126D and 74HC165D,653 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 5 V or 3.3 V logic system.
What is the function of the output enable pins on the 74HC126D?
The 74HC126D has four independent active-HIGH output enable (OE) pins, one for each buffer. When an OE pin is HIGH, the corresponding buffer output is active; when LOW, the output is placed in a high-impedance state, allowing the device to drive a shared bus without contention.
How does the 74HC165D,653 handle parallel data loading and serial shifting?
The 74HC165D,653 loads eight parallel data bits asynchronously when the parallel load input (PL) is LOW. When PL is HIGH, the device shifts data from the parallel inputs to the serial output (Q7) on each LOW-to-HIGH transition of the clock (CP), with the serial input (DS) allowing cascading of multiple devices.
Do both devices support cascading for expanded logic functions?
Only the 74HC165D,653 supports cascading. Its serial input (DS) and complementary serial output (Q7) allow multiple shift registers to be chained for wider parallel-to-serial conversion. The 74HC126D is a buffer/line driver and does not have cascading provisions.
What are the typical propagation delays for the 74HC126D and 74HC165D,653 at 5 V?
At 5 V supply, the 74HC126D typically exhibits a propagation delay of approximately 10 ns to 15 ns from input to output. The 74HC165D,653 typically exhibits a propagation delay of approximately 13 ns to 20 ns for clock-to-output transitions. Exact values depend on load capacitance and are specified in the respective manufacturer datasheets.
Are the 74HC126D and 74HC165D,653 available in the same package type?
No. The 74HC126D is commonly offered in a 14-pin SOIC package (the "D" suffix indicates SOIC). The 74HC165D,653 is offered in a 16-pin SOIC package. The different pin counts and package sizes prevent physical interchangeability on a PCB.