Part A
74HC139D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 4290 Stückzahl
- Package
- SOIC-16
- Series
- Logic.Signal Schalter, Multiplexer, Decoder
Replacement verdict
Not a drop-in replacement
The 74HC164D and 74HC139D are not functionally interchangeable despite sharing the same 74HC logic family and SOIC-14 package. The 74HC164D is an 8-bit serial-in/parallel-out shift register, while the 74HC139D is a dual 2-to-4 line decoder/demultiplexer. Their internal architectures, pin functions, and logic operations are fundamentally different, making direct substitution impossible without complete circuit redesign.
Different logic function
Different input type
Different output type
Different pin function
Parts at a glance
Part B
74HC164D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 2726 Stückzahl
- Package
- SOIC-8
- Series
- Logic-Shift-Register
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC164D | 74HC139D | Why it matters |
|---|---|---|---|
| Logic Function | 8-bit serial-in/parallel-out shift register | Dual 2-to-4 line decoder/demultiplexer | The core function determines whether the device can be substituted at all; these two ICs perform fundamentally different logic operations. |
| Number of Outputs | 8 parallel outputs | 8 outputs (two groups of 4) | Output count and grouping affect how many loads can be driven and how the device maps to a given circuit topology. |
| Input Type | Serial data inputs with clock | 2 address inputs per decoder plus enable | Input signaling scheme dictates the driving logic and timing requirements in the surrounding circuit. |
| Output Type | Parallel data outputs | Active-LOW decoded outputs | Output polarity and behavior determine compatibility with downstream logic and whether inversion is required. |
| Clock Requirement | Requires clock for shifting | Combinational, no clock | Clocked versus combinational operation changes timing analysis and maximum operating frequency considerations. |
| Propagation Delay (typical) | Approximately 14 ns at 4.5 V | Approximately 11 ns at 4.5 V | Propagation delay influences maximum system speed and timing margins in synchronous designs. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Matching supply ranges ensures both devices can operate in the same power domain without level shifting. |
| Package | SO14 | SO16 | Package footprint and pin count must match the PCB layout for a drop-in replacement. |
| Logic Family | HC (High-speed CMOS) | HC (High-speed CMOS) | Same logic family ensures compatible input thresholds, output drive, and noise immunity. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical temperature ratings allow use in the same environmental conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC139D | 74HC164D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Obsolete | Active |
| Type | Decoder/Demultiplexer | - |
| Circuit | 1 x 2:4 | - |
| Independent Circuits | 2 | - |
| Current - Output High Low | 5.2mA, 5.2mA | - |
| Voltage Supply Source | Single Supply | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | - | Shift Register |
| Output Type | - | Push-Pull |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Function | - | Serial to Parallel |
Frequently asked questions
What are the primary functions of the 74HC164D and 74HC139D?
The 74HC164D is an 8-bit serial-in/parallel-out shift register with a synchronous clear input. The 74HC139D is a dual 2-to-4 line decoder/demultiplexer with active-low enable inputs.
Can the 74HC164D and 74HC139D be used interchangeably in a circuit?
No. They perform fundamentally different logic functions. The 74HC164D shifts serial data to parallel outputs, while the 74HC139D decodes a 2-bit binary input into one of four mutually exclusive outputs. They are not pin-compatible or functionally equivalent.
What are the package and pin count differences between the 74HC164D and 74HC139D?
Both devices are typically offered in a 16-pin SOIC package (the "D" suffix in Nexperia and similar manufacturer naming denotes SOIC-16). However, their pinouts differ because their internal logic functions are different. Always consult the specific manufacturer datasheet for the exact pin assignment.
What supply voltage range do the 74HC164D and 74HC139D support?
Both are 74HC-series CMOS devices and typically operate over a supply voltage range of 2.0 V to 6.0 V. Verify the exact recommended operating conditions in the manufacturer datasheet for the specific part number and temperature grade.
How do the propagation delays of the 74HC164D and 74HC139D compare?
Propagation delay depends on supply voltage, load capacitance, and temperature. In general, the 74HC139D decoder has a shorter typical propagation delay from address inputs to outputs than the 74HC164D shift register has from clock to parallel outputs. Use the manufacturer datasheet timing tables for guaranteed limits.
What is the difference in output drive capability between the 74HC164D and 74HC139D?
Both devices are standard 74HC CMOS outputs and typically provide symmetrical source/sink drive in the range of ±4 mA to ±5.2 mA at 4.5 V to 6.0 V. Confirm the exact output current ratings in the manufacturer datasheet, as they may vary slightly by vendor and test condition.
Are the 74HC164D and 74HC139D available in automotive-qualified versions?
Automotive qualification depends on the specific manufacturer and part number suffix. Some vendors offer AEC-Q100 qualified versions of 74HC logic devices, but the standard 74HC164D and 74HC139D may not be automotive-qualified. Check the manufacturer's product page and datasheet for qualification status.
Which device is better for expanding microcontroller I/O, the 74HC164D or 74HC139D?
The 74HC164D is generally used to expand outputs by converting serial data from a microcontroller into parallel outputs. The 74HC139D is used to select one of four outputs based on a 2-bit address, which is useful for chip-select or address decoding. The choice depends on whether the application requires serial-to-parallel conversion or address decoding.