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 74HCT125D-Q100J are not functionally interchangeable. The 74HCT540D is an octal inverting buffer with 3-state outputs, while the 74HCT125D-Q100J is a quad non-inverting buffer with 3-state outputs. They differ in logic function, channel count, package footprint, and pinout, so direct substitution is not possible without circuit redesign.
Different logic function
Different channel count
Different package footprint
Different pinout
Parts at a glance
Part B
74HCT125D-Q100J
Nexperia USA Inc.
- Lifecycle
- Active
- Stock
- 9544 Stückzahl
- Package
- SOIC-14
- Series
- Logic c Puffer, Treiber, Empfänger, Transceiver
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 | 74HCT125D-Q100J | Why it matters |
|---|---|---|---|
| Logic Function | Octal buffer/line driver with 3-state outputs, inverting | Quad buffer/line driver with 3-state outputs, non-inverting | The logic function determines signal polarity and channel count, directly affecting circuit behavior and pin compatibility. |
| Number of Channels | 8 | 4 | Channel count determines how many independent signal lines can be buffered, affecting board layout and device count. |
| Output Type | 3-state, inverting | 3-state, non-inverting | Output polarity must match the intended logic to avoid signal inversion errors in the target design. |
| Control Inputs | Two active-low output enable pins (OE1, OE2) | Four active-low output enable pins (one per channel) | Enable pin configuration affects how outputs are gated and whether channels can be controlled independently. |
| Package | SO20 (20-pin SOIC) | SO14 (14-pin SOIC) | Package footprint and pin count must match the PCB layout for physical substitutability. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both devices operate in the standard 5 V TTL-compatible range, ensuring supply compatibility. |
| Logic Family | HCT (High-speed CMOS, TTL-compatible) | HCT (High-speed CMOS, TTL-compatible) | Same logic family ensures compatible input thresholds and output drive characteristics. |
| Qualification | Standard commercial/industrial | AEC-Q100 qualified (automotive grade) | Automotive qualification indicates enhanced reliability and temperature range for harsh environments. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C (AEC-Q100 Grade 1) | Temperature range affects suitability for automotive and industrial applications. |
| Propagation Delay (typical) | ~12 ns at 5 V | ~12 ns at 5 V | Propagation delay impacts timing margins in high-speed digital circuits. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT540D | 74HCT125D-Q100J |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HCT | Automotive, AEC-Q100, 74HCT |
| Part Status | Active | Active |
| Logic Type | Buffer, Inverting | Buffer, Non-Inverting |
| Number of Elements | 1 | 4 |
| Number of Bits per Element | 8 | 1 |
| Output Type | 3-State | 3-State |
| Current - Output High Low | 6mA, 6mA | 6mA, 6mA |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Operating Temperature | -40°C ~ 85°C (TA) | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the main functional differences between the 74HCT540D and the 74HCT125D-Q100J?
The 74HCT540D is an octal inverting buffer/line driver with 3-state outputs, featuring two active-low output enable pins that control four outputs each. The 74HCT125D-Q100J is a quad non-inverting buffer/line driver with 3-state outputs, where each of the four buffers has its own independent active-low output enable pin. The 74HCT540D provides eight inverting channels, while the 74HCT125D-Q100J provides four non-inverting channels.
Are the 74HCT540D and 74HCT125D-Q100J pin-compatible?
No. The 74HCT540D is typically supplied in a 20-pin package (SO20 or TSSOP20), while the 74HCT125D-Q100J is supplied in a 14-pin package (SO14). They have different pin counts, pin assignments, and package footprints, so they are not pin-compatible and cannot be used as drop-in replacements for each other.
What is the difference in output logic polarity between these two devices?
The 74HCT540D provides inverting outputs, meaning the output logic level is the inverse of the input. The 74HCT125D-Q100J provides non-inverting outputs, meaning the output logic level follows the input. This polarity difference is critical when selecting a replacement for signal path integrity.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HCT540D and the 74HCT125D-Q100J are HCT-family CMOS logic devices designed to operate from a nominal 5 V supply, with a specified operating supply voltage range typically from 4.5 V to 5.5 V. They are also TTL-voltage compatible at their inputs.
What is the difference in the number of 3-state output enable controls?
The 74HCT540D has two active-low output enable pins (OE1 and OE2), each controlling a group of four outputs. The 74HCT125D-Q100J has four independent active-low output enable pins (1OE through 4OE), one for each of its four buffers. This gives the 74HCT125D-Q100J more granular control over individual channels.
Is the 74HCT125D-Q100J qualified for automotive applications while the 74HCT540D is not?
The 74HCT125D-Q100J carries the Q100 suffix, which indicates it is qualified to the AEC-Q100 standard for automotive-grade integrated circuits. The 74HCT540D, as a standard logic part without the Q100 designation, is not automatically AEC-Q100 qualified. Designers requiring automotive qualification should verify the specific ordering code and qualification status of each device.
Can the 74HCT540D drive higher output currents than the 74HCT125D-Q100J?
Both devices are standard HCT-family logic buffers with similar output drive characteristics, typically specified with a symmetric output drive of ±4 mA or ±6 mA depending on the manufacturer and test conditions. Neither device is intended as a high-current driver. For specific drive current ratings, consult the respective manufacturer datasheet, as values may vary slightly between suppliers.
Which device is more suitable for bidirectional bus applications?
Neither device is inherently a bidirectional transceiver. The 74HCT540D is an octal buffer with 3-state outputs suitable for unidirectional bus driving with enable control. The 74HCT125D-Q100J is a quad buffer with independent 3-state outputs, also unidirectional per channel. For true bidirectional bus applications, a dedicated transceiver such as the 74HCT245 would be more appropriate.