Part A
74HCT540D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 1645 Stückzahl
- Package
- SOIC-14
- Series
- Logic c Puffer, Treiber, Empfänger, Transceiver
Replacement verdict
Not a drop-in replacement
The 74HCT540D and 74HCT123D-Q100J are functionally unrelated devices and cannot serve as substitutes for one another. The 74HCT540D is an octal inverting buffer/line driver with 3-state outputs, while the 74HCT123D-Q100J is a dual retriggerable monostable multivibrator. They differ in logic function, channel configuration, output behavior, and package footprint, making direct replacement impossible without a complete circuit redesign.
Different logic function
Different channel count
Different output type
Different package footprint
Parts at a glance
Part B
74HCT123D-Q100J
Nexperia USA Inc.
- Lifecycle
- Active
- Stock
- 7163 Stückzahl
- Package
- SOIC-16
- Series
- Logic-Multivibrators
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT540D | 74HCT123D-Q100J | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver with 3-state outputs (inverting) | Dual Retriggerable Monostable Multivibrator | The core logic function determines whether the parts can substitute each other in a circuit; these devices perform completely different functions. |
| Number of Channels | 8 | 2 | Channel count affects how many signals can be processed simultaneously, impacting circuit design and board layout. |
| Output Type | 3-state, inverting | Push-pull (standard CMOS) | Output configuration determines bus compatibility and whether outputs can be shared on a common data line. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both operate in the standard 5 V TTL-compatible range, so supply compatibility is not a differentiator here. |
| Propagation Delay | Typically 12 ns at 5 V | Typically 25 ns at 5 V | Propagation delay affects timing margins and maximum operating frequency in synchronous systems. |
| Package Type | SO16 (SOIC-16) | SO16 (SOIC-16) | Package compatibility is essential for drop-in replacement on an existing PCB footprint. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Temperature range determines suitability for automotive and industrial environments. |
| Automotive Qualification | Not AEC-Q100 qualified | AEC-Q100 qualified | AEC-Q100 qualification is mandatory for automotive applications and indicates enhanced reliability testing. |
| Output Drive Current | ±6 mA | ±4 mA | Drive current determines the ability to drive loads and fan-out to other logic inputs. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT540D | 74HCT123D-Q100J |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HCT | Automotive, AEC-Q100, 74HCT |
| Part Status | Active | Active |
| Logic Type | Buffer, Inverting | Monostable |
| Independent Circuits | - | 2 |
| Schmitt Trigger Input | - | Yes |
| Propagation Delay | - | 65 ns |
| Current - Output High Low | 6mA, 6mA | 4mA, 4mA |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5 V ~ 5.5 V |
| Operating Temperature | -40°C ~ 85°C (TA) | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Elements | 1 | - |
| Number of Bits per Element | 8 | - |
| Output Type | 3-State | - |
Frequently asked questions
What are the primary functional differences between the 74HCT540D and the 74HCT123D-Q100J?
The 74HCT540D is an octal inverting buffer/line driver with 3-state outputs, designed for bus-oriented applications. The 74HCT123D-Q100J is a dual retriggerable monostable multivibrator (one-shot) that generates output pulses of a specified duration determined by external timing components. They serve entirely different logic functions and are not functionally interchangeable.
Are the 74HCT540D and 74HCT123D-Q100J pin-compatible?
No. The 74HCT540D is typically supplied in a 20-pin package (e.g., SO20 or TSSOP20) with pin functions dedicated to eight buffer channels, two active-low output enables, and power pins. The 74HCT123D-Q100J is typically supplied in a 16-pin package (e.g., SO16 or TSSOP16) with pins for two independent monostable multivibrator sections, each having trigger, reset, timing, and output pins. The pin counts and pin functions differ, so they are not pin-compatible.
Can the 74HCT540D and 74HCT123D-Q100J operate from the same supply voltage?
Yes. Both devices are members of the 74HCT logic family and are specified for a nominal supply voltage of 5 V, with a recommended operating range typically from 4.5 V to 5.5 V. However, always verify the exact limits in the respective manufacturer datasheets, as they may differ slightly between vendors.
Does the 74HCT123D-Q100J have automotive qualification while the 74HCT540D does not?
The suffix "-Q100" in 74HCT123D-Q100J indicates that the device is qualified to the AEC-Q100 standard for automotive applications, as defined by the manufacturer. The 74HCT540D, as a standard logic part number without the Q100 suffix, is not automatically automotive-qualified. Automotive qualification must be confirmed from the specific manufacturer's datasheet or product page for each device.
What is the difference in output drive capability between the 74HCT540D and the 74HCT123D-Q100J?
The 74HCT540D is specified with standard 74HCT output drive, typically ±6 mA at 5 V, suitable for driving bus lines and moderate loads. The 74HCT123D-Q100J also provides standard 74HCT output drive, typically ±4 mA to ±6 mA depending on the manufacturer and test conditions. For critical designs, consult the specific datasheet for the guaranteed output current ratings, as they may vary between manufacturers.
Can the 74HCT540D be used to replace the 74HCT123D-Q100J in a pulse-generation circuit?
No. The 74HCT540D is a buffer/line driver and cannot generate timed output pulses. The 74HCT123D-Q100J is a monostable multivibrator specifically designed to produce output pulses of a defined width set by external resistors and capacitors. Replacing one with the other would not provide the required pulse-generation function.
Do both devices support 3-state outputs?
No. The 74HCT540D features 3-state outputs that can be placed in a high-impedance state via the output enable pins, allowing connection to a shared bus. The 74HCT123D-Q100J has standard push-pull outputs and does not provide a high-impedance output state. This difference is critical when interfacing to shared signal lines.
Are the timing characteristics of the 74HCT123D-Q100J dependent on external components?
Yes. The output pulse width of each monostable section in the 74HCT123D-Q100J is determined by an external resistor (Rext) and capacitor (Cext) connected to the corresponding timing pins. The 74HCT540D has no such timing function; its propagation delay is a fixed characteristic specified in the datasheet and is not adjustable by external components.