Part A
74HC123D
NXP USA Inc.
- Lifecycle
- Active
- Stock
- 3320 PCS
- Package
- SOIC-16
- Series
- Lógica - Multivibradores
Replacement verdict
Not a drop-in replacement
The 74HC123D and 74HC154D,652 serve fundamentally different logic functions and cannot be used interchangeably in existing designs. The 74HC123D is a dual retriggerable monostable multivibrator for pulse generation, while the 74HC154D,652 is a 4-to-16 line decoder/demultiplexer for address decoding. Their divergent functional architectures, pin configurations, and signal path requirements make direct substitution impossible without complete circuit redesign.
Different logic function
Different input/output configuration
Different pin assignment
Different application circuit
Parts at a glance
Part B
74HC154D,652
NXP USA Inc.
- Lifecycle
- Active
- Stock
- 2528 PCS
- Package
- SOIC-24
- Series
- Lógica - Conmutadores de sinais, Multiplexers, Decodificadores
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC123D | 74HC154D,652 | Why it matters |
|---|---|---|---|
| Function | Dual retriggerable monostable multivibrator with reset | 4-to-16 line decoder/demultiplexer | The core logic function differs completely, so these parts are not functionally interchangeable in a circuit. |
| Logic Type | Monostable multivibrator | Decoder/Demultiplexer | Determines the signal-processing behavior and the role the IC plays in a design. |
| Number of Circuits | 2 | 1 | Affects how many independent timing or decoding channels are available per package. |
| Number of Inputs | 2 trigger inputs per multivibrator (plus reset) | 4 address inputs (plus enable inputs) | Input count defines the control signals required and the addressing or triggering capability. |
| Number of Outputs | 2 outputs per multivibrator (Q and Qbar) | 16 outputs | Output count determines how many loads or lines the device can drive. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both share the HC-family supply range, so voltage compatibility is similar. |
| Propagation Delay | Approximately 20 ns typical at 5 V | Approximately 20 ns typical at 5 V | Delay influences timing margins and maximum operating frequency in high-speed designs. |
| Output Current | ±4 mA typical at 5 V | ±4 mA typical at 5 V | Drive strength affects fan-out and whether external buffering is needed. |
| Package Type | SOIC-16 | SOIC-24 | Different pin counts and package sizes prevent direct drop-in replacement on the same PCB footprint. |
| Pin Count | 16 | 24 | Pin count mismatch means the devices cannot share the same socket or layout. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC123D | 74HC154D,652 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Type | - | Decoder/Demultiplexer |
| Circuit | - | 1 x 4:16 |
| Independent Circuits | 2 | 1 |
| Current - Output High Low | 5.2mA, 5.2mA | 5.2mA, 5.2mA |
| Voltage Supply Source | - | Single Supply |
| Voltage - Supply | 2 V ~ 6 V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | Monostable | - |
| Schmitt Trigger Input | Yes | - |
| Propagation Delay | 40 ns | - |
Frequently asked questions
What are the primary functions of the 74HC123D and the 74HC154D,652?
The 74HC123D is a dual retriggerable monostable multivibrator that generates a precise output pulse width determined by an external resistor and capacitor. The 74HC154D,652 is a 4-to-16 line decoder/demultiplexer that accepts a 4-bit binary address and activates one of 16 mutually exclusive outputs.
Can the 74HC123D and 74HC154D,652 be used interchangeably in a design?
No. They perform fundamentally different logic functions. The 74HC123D is a timing device for pulse generation, while the 74HC154D,652 is a combinational logic decoder/demultiplexer. They are not pin-compatible or functionally equivalent and cannot be substituted for one another.
What are the package and pin count differences between the 74HC123D and the 74HC154D,652?
The 74HC123D is typically supplied in a 16-pin SOIC package. The 74HC154D,652 is supplied in a 24-pin SOIC package. The different pin counts and pinouts prevent any direct PCB footprint compatibility between the two devices.
What supply voltage range do the 74HC123D and 74HC154D,652 support?
Both devices are members of the 74HC high-speed CMOS family and operate over a specified supply voltage range of 2.0 V to 6.0 V. Typical operation is at 5.0 V, but both parts are characterized for the full 2.0 V to 6.0 V range per their respective manufacturer datasheets.
How does the output drive capability compare between the 74HC123D and the 74HC154D,652?
Both devices provide standard 74HC CMOS output drive. The 74HC123D outputs can source or sink approximately 4 mA at 5 V. The 74HC154D,652 outputs provide similar standard CMOS drive, typically 4 mA at 5 V. Neither device is a high-current driver; external buffering is required for loads exceeding the specified output current.
Are the 74HC123D and 74HC154D,652 compatible with 74LS or 74HCT logic levels?
The 74HC123D and 74HC154D,652 are 74HC family devices with CMOS input thresholds that are supply-voltage dependent. They are not directly compatible with 74LS TTL logic levels at 5 V without level shifting. For direct TTL-level compatibility, the corresponding 74HCT versions should be selected instead.
What are the typical propagation delay characteristics of the 74HC123D and 74HC154D,652?
The 74HC123D output pulse width is set by the external RC network, not by a fixed propagation delay. The 74HC154D,652 has a typical address-to-output propagation delay of approximately 20 ns at 5 V. Exact timing values should be verified from the specific manufacturer datasheet for the intended operating voltage and temperature.
Which applications are best suited for the 74HC123D versus the 74HC154D,652?
The 74HC123D is suited for pulse stretching, debouncing, timing generation, and retriggerable one-shot functions. The 74HC154D,652 is suited for memory address decoding, I/O port selection, and demultiplexing a single data line to one of sixteen outputs. The choice depends entirely on whether the system requires timing or decoding functionality.