Part A
74HCT540D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 1645 PCS
- Package
- SOIC-14
- Series
- Logique - Buffers, lecteurs, récepteurs, émetteurs - récepteurs
Replacement verdict
Not a drop-in replacement
The 74HCT540D and 74HCT04D,653 are not functionally interchangeable. The 74HCT540D is an octal inverting buffer with 3-state outputs, while the 74HCT04D,653 is a hex inverter with standard totem-pole outputs. They differ in channel count, output configuration, enable control, and pinout, so direct substitution is not possible without circuit redesign.
Different channel count
Different output type
Different enable control
Different pinout
Parts at a glance
Part B
74HCT04D,653
NXP semiconducteurs
- Lifecycle
- Active
- Stock
- 9812 PCS
- Series
- Logique - portes et Onduleurs
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 | 74HCT04D,653 | Why it matters |
|---|---|---|---|
| Logic Function | Octal buffer/line driver with 3-state outputs (inverting) | Hex inverter (unbuffered) | Defines the core signal-processing behavior; these devices perform fundamentally different logic operations and cannot be substituted directly. |
| Number of Channels | 8 | 6 | Channel count determines how many independent signal lines can be handled by a single package. |
| Output Type | 3-state | Push-pull | 3-state outputs allow bus sharing and high-impedance isolation, while push-pull outputs cannot be tied together on a shared bus. |
| Logic Polarity | Inverting | Inverting | Both invert, but the 540 also inverts during buffering; polarity must match the surrounding logic to preserve signal integrity. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both are HCT-family parts designed for 5 V TTL-compatible systems; identical supply range supports similar power design. |
| Propagation Delay (typical) | ~14 ns at 5 V | ~9 ns at 5 V | Propagation delay affects timing margins in synchronous and high-speed digital circuits. |
| Output Drive Current | ±6 mA | ±4 mA | Drive current determines fan-out and the ability to drive loads such as LEDs or long traces. |
| Package | SO-20 (20-pin SOIC) | SO-14 (14-pin SOIC) | Different pin counts and footprints prevent direct PCB drop-in replacement. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both support industrial temperature ranges, making them suitable for similar environmental conditions. |
| Input Compatibility | TTL-compatible | TTL-compatible | TTL-compatible inputs allow direct interfacing with 5 V TTL logic without additional level shifting. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT540D | 74HCT04D,653 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74HCT | 74HCT |
| Part Status | Active | Active |
| Logic Type | Buffer, Inverting | Inverter |
| Number of Circuits | - | 6 |
| Number of Inputs | - | 1 |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Max) | - | 2 µA |
| Current - Output High Low | 6mA, 6mA | 4mA, 4mA |
| Logic Level - Low | - | 0.8V |
| Logic Level - High | - | 2V |
| Max Propagation Delay @ V Max CL | - | 19ns @ 4.5V, 50pF |
| 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 74HCT04D,653?
The 74HCT540D is an octal inverting buffer/line driver with 3-state outputs, while the 74HCT04D,653 is a hex inverter with standard push-pull outputs. The 74HCT540D provides eight inverting channels with tri-state control for bus-oriented applications, whereas the 74HCT04D,653 provides six inverting channels without tri-state capability.
Are the 74HCT540D and 74HCT04D,653 pin-compatible?
No. The 74HCT540D is typically supplied in a 20-pin SOIC package, while the 74HCT04D,653 is supplied in a 14-pin SOIC package. They have different pin counts, pinouts, and package dimensions, so they are not drop-in replacements for each other.
Can the 74HCT540D and 74HCT04D,653 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.
Does the 74HCT540D have 3-state outputs while the 74HCT04D,653 does not?
Yes. The 74HCT540D features 3-state outputs controlled by two active-low output enable pins, allowing the outputs to be placed in a high-impedance state for bus sharing. The 74HCT04D,653 has standard totem-pole outputs that are always active and cannot be tri-stated.
What is the difference in channel count between the 74HCT540D and the 74HCT04D,653?
The 74HCT540D contains eight inverting buffer channels, while the 74HCT04D,653 contains six inverting channels. This difference affects the number of signals that can be buffered or inverted in a given design.
Are both the 74HCT540D and 74HCT04D,653 TTL-input compatible?
Yes. Both devices are HCT-type logic, which means they have TTL-compatible input thresholds while operating from a 5 V CMOS supply, allowing direct interfacing with TTL logic levels.
Which device is more suitable for driving a shared data bus?
The 74HCT540D is more suitable for shared bus applications because its 3-state outputs can be disabled to high impedance, preventing bus contention. The 74HCT04D,653 lacks 3-state outputs and is therefore not intended for direct connection to a shared bus without external isolation.
Do the 74HCT540D and 74HCT04D,653 have the same output drive strength?
Both devices are specified with standard 74HCT output drive characteristics, typically capable of sourcing and sinking several milliamperes. However, exact drive current ratings should be verified from the respective manufacturer datasheets, as they may differ between the octal buffer and hex inverter implementations.