Part A
74HC138D
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 2131 PCS
- Package
- SOIC-16
- Series
- Logic - Signal Switches, Multiplexers, Decoders
Replacement verdict
Not a drop-in replacement
The 74HC14D,653 and 74HC138D are not functionally interchangeable. The 74HC14D,653 is a hex inverting Schmitt trigger, while the 74HC138D is a 3-to-8 line decoder/demultiplexer. They differ in logic function, input/output configuration, channel count, and pinout, so direct substitution is not possible without a complete circuit redesign.
Different logic function
Different channel count
Different pinout
Different output configuration
Parts at a glance
Part B
74HC14D,653
Nexperia Hoa Kỳ Inc.
- Lifecycle
- Active
- Stock
- 3794 PCS
- Package
- SOIC-14
- Series
- Logic - Gates and Inverters
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC14D,653 | 74HC138D | Why it matters |
|---|---|---|---|
| Logic Function | Hex inverting Schmitt trigger | 3-to-8 line decoder/demultiplexer | Defines the core function; these devices are not functionally interchangeable. |
| Number of Channels / Outputs | 6 inverters | 8 outputs (from 3 inputs) | Determines how many signals can be processed or selected in a design. |
| Input Type | Schmitt trigger inputs | Standard CMOS inputs | Schmitt trigger inputs provide hysteresis for noisy or slow signals, which standard inputs do not. |
| Output Type | Inverting | Active-low (inverting) outputs | Output polarity affects signal conditioning and downstream logic compatibility. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both support the same HC-family supply range, allowing use in similar logic-level systems. |
| Propagation Delay (typical) | ~13 ns at 4.5 V | ~15 ns at 4.5 V | Affects maximum operating speed and timing margins in synchronous designs. |
| Package | SO-14 (SOIC-14) | SO-16 (SOIC-16) | Different pin counts and footprints prevent direct PCB drop-in replacement. |
| Pin Count | 14 | 16 | Pin count determines package compatibility and available I/O. |
| Enable / Control Inputs | None | 3 enable inputs (two active-low, one active-high) | Enable inputs allow cascading and output gating, which the inverter array lacks. |
| Typical Application | Signal conditioning, debouncing, oscillators | Address decoding, memory/IO selection, demultiplexing | Highlights the distinct roles these ICs play in digital systems. |
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Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC138D | 74HC14D,653 |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Type | Decoder/Demultiplexer | - |
| Circuit | 1 x 3:8 | - |
| Independent Circuits | 1 | - |
| Current - Output High Low | 5.2mA, 5.2mA | 5.2mA, 5.2mA |
| Voltage Supply Source | Single Supply | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | - | Inverter |
| Number of Circuits | - | 6 |
| Number of Inputs | - | 1 |
| Features | - | Schmitt Trigger |
| Current - Quiescent (Max) | - | 2 µA |
| Logic Level - Low | - | 0.3V ~ 1.2V |
| Logic Level - High | - | 1.5V ~ 4.2V |
| Max Propagation Delay @ V Max CL | - | 21ns @ 6V, 50pF |
Frequently asked questions
What are the primary functions of the 74HC14D,653 and the 74HC138D?
The 74HC14D,653 is a hex inverting Schmitt trigger, used for signal conditioning and waveform shaping of slow or noisy digital inputs. The 74HC138D is a 3-to-8 line decoder/demultiplexer, used for address decoding and data routing in digital systems.
Can the 74HC14D,653 and 74HC138D be used interchangeably?
No. They perform fundamentally different logic functions. The 74HC14D,653 provides six independent Schmitt-trigger inverters, while the 74HC138D decodes a 3-bit binary address into eight mutually exclusive active-low outputs. They are not pin-compatible or functionally equivalent.
What are the package and pin count differences between the 74HC14D,653 and 74HC138D?
The 74HC14D,653 is supplied in a 14-pin SOIC package (SO14). The 74HC138D is supplied in a 16-pin SOIC package (SO16). The different pin counts and pinouts prevent direct PCB substitution.
What supply voltage range do the 74HC14D,653 and 74HC138D support?
Both devices are 74HC-family CMOS logic parts and operate over a supply voltage range of 2.0 V to 6.0 V, with typical operation at 5.0 V. This is specified in the respective manufacturer datasheets.
How do the propagation delays of the 74HC14D,653 and 74HC138D compare?
At a 5 V supply, the 74HC14D,653 typically exhibits a propagation delay of approximately 13 ns to 25 ns depending on the transition direction and load. The 74HC138D typically exhibits a propagation delay of approximately 20 ns to 30 ns from address or enable inputs to outputs. Exact values vary with load capacitance and supply voltage per the datasheets.
What are the output drive capabilities of the 74HC14D,653 and 74HC138D?
Both devices provide standard 74HC CMOS output drive, typically ±4 mA at 5 V. The 74HC14D,653 outputs are push-pull inverting Schmitt triggers. The 74HC138D outputs are active-low and also push-pull. Neither device is intended for high-current load driving.
Are the 74HC14D,653 and 74HC138D available in other package options?
Yes. The 74HC14D,653 is also available in other packages such as TSSOP and DIP under different order codes. The 74HC138D is also available in TSSOP and DIP under different order codes. The specific suffix "D,653" and "D" indicate SOIC packaging from the respective manufacturer.
Which device is better for debouncing a mechanical switch?
The 74HC14D,653 is the appropriate choice for debouncing mechanical switches because its Schmitt-trigger inputs provide hysteresis, which cleanly squares up slow or noisy edges. The 74HC138D does not have Schmitt-trigger inputs and is not intended for switch debouncing.
Can the 74HC138D be used to expand the output count of a microcontroller?
Yes. The 74HC138D can decode three microcontroller output lines into eight active-low outputs, effectively expanding the number of selectable peripheral or memory chip-select lines. The 74HC14D,653 cannot perform this function because it only inverts and conditions signals.