Part A
74VHC595MX
Công ty bán dẫn Fairchild
- Lifecycle
- Active
- Stock
- 3740 PCS
- Package
- SOIC-16
- Series
- Logic - Shift Registers
Replacement verdict
Not a drop-in replacement
The 74VHC595MX and 74VHC123AMX are functionally unrelated devices and cannot serve as substitutes for one another. The 74VHC595MX is an 8-bit serial-in/parallel-out shift register with output latches, while the 74VHC123AMX is a dual retriggerable monostable multivibrator. Their internal architectures, logic functions, pin assignments, and intended applications are fundamentally different, making cross-replacement technically infeasible in any design.
Different logic function
Different output type
Different pinout
Different application
Parts at a glance
Part B
74VHC123AMX
onsemi
- Lifecycle
- Active
- Stock
- 2754 PCS
- 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 | 74VHC595MX | 74VHC123AMX | Why it matters |
|---|---|---|---|
| Function | 8-bit serial-in/parallel-out shift register with output latches | Dual retriggerable monostable multivibrator | The core logic function differs, so these devices are not functionally interchangeable in a circuit. |
| Logic Family | VHC (Very High Speed CMOS) | VHC (Very High Speed CMOS) | Same logic family means compatible voltage levels and similar switching characteristics. |
| Supply Voltage Range | 2.0 V to 5.5 V | 2.0 V to 5.5 V | Both support the same operating voltage window, allowing use in 3.3 V and 5 V systems. |
| Number of Pins | 16 | 16 | Same pin count, but pinout and function differ, so direct drop-in replacement is not possible. |
| Package Type | SOIC-16 | SOIC-16 | Identical package allows the same PCB footprint, but electrical function still differs. |
| Output Type | 3-state parallel outputs | Push-pull pulse outputs | Output behavior differs significantly, affecting how each device drives downstream circuitry. |
| Propagation Delay | Approximately 6 ns at 5 V | Approximately 10 ns at 5 V | Timing differences affect maximum operating frequency and signal integrity in high-speed designs. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Both support industrial temperature ranges, suitable for similar environmental conditions. |
| Primary Application | Serial-to-parallel data conversion, LED driving, GPIO expansion | Pulse generation, timing control, one-shot delays | Intended use cases are fundamentally different, confirming they are not substitutes. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC595MX | 74VHC123AMX |
|---|---|---|
| Supplier | - | onsemi |
| Series | 74VHC | 74VHC |
| Part Status | Active | Active |
| Logic Type | Shift Register | Monostable |
| Independent Circuits | - | 2 |
| Schmitt Trigger Input | - | Yes |
| Propagation Delay | - | 8.1 ns |
| Current - Output High Low | - | 8mA, 8mA |
| Voltage - Supply | 2V ~ 5.5V | 2 V ~ 5.5 V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Output Type | Tri-State | - |
| Number of Elements | 1 | - |
| Number of Bits per Element | 8 | - |
| Function | Serial to Parallel, Serial | - |
Frequently asked questions
What are the primary functions of the 74VHC595MX and 74VHC123AMX?
The 74VHC595MX is an 8-bit serial-in, parallel-out shift register with output latches and 3-state outputs. The 74VHC123AMX is a dual retriggerable monostable multivibrator designed to generate precise output pulses.
Can the 74VHC595MX and 74VHC123AMX be used interchangeably in a design?
No. They perform fundamentally different logic functions. The 74VHC595MX is a shift register for serial-to-parallel data conversion, while the 74VHC123AMX is a monostable multivibrator for pulse generation. They are not pin-compatible or functionally equivalent.
What are the operating voltage ranges for these devices?
Both the 74VHC595MX and 74VHC123AMX operate over a supply voltage range of 2.0 V to 5.5 V, typical of the VHC logic family.
What package types are available for the 74VHC595MX and 74VHC123AMX?
The 74VHC595MX is offered in a 16-pin SOIC package. The 74VHC123AMX is also offered in a 16-pin SOIC package. Both are surface-mount devices.
What are the output drive capabilities of the 74VHC595MX?
The 74VHC595MX provides standard VHC output drive, typically ±8 mA at 5 V VCC, suitable for driving low-power logic inputs and indicators.
What is the function of the retriggerable feature on the 74VHC123AMX?
The retriggerable feature allows the output pulse to be extended by applying additional trigger pulses before the timing period expires, enabling longer output pulses without external timing component changes.
Are external timing components required for the 74VHC123AMX?
Yes. The 74VHC123AMX requires an external resistor (REXT) and capacitor (CEXT) for each monostable channel to set the output pulse width.
What is the maximum operating frequency of the 74VHC595MX?
The 74VHC595MX supports shift frequencies up to 100 MHz at 5 V VCC, as specified in the manufacturer datasheet.