Part A
74HC238D
Toshiba Semiconductor and Storage
- Lifecycle
- Active
- Stock
- 5394 PCS
- Package
- SOIC-16
- Series
- Lógica - Conmutadores de sinais, Multiplexers, Decodificadores
Replacement verdict
Not a drop-in replacement
The 74HC245D and 74HC238D are not functionally interchangeable despite sharing the same 74HC logic family and SOIC-16 package. The 74HC245D is an octal bidirectional bus transceiver with three-state outputs, while the 74HC238D is a 3-to-8 line decoder/demultiplexer with active-low outputs. Their internal logic functions, pin assignments, and signal flow directions are fundamentally different, making direct substitution impossible without complete circuit redesign.
Different logic function
Different pin assignment
Different output type
Different signal direction
Parts at a glance
Part B
74HC245D
Toshiba Semiconductor and Storage
- Lifecycle
- Active
- Stock
- 4218 PCS
- Package
- SOIC-14
- Series
- Lógica - Buffers, Drivers, Receivers, Transceivers
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC245D | 74HC238D | Why it matters |
|---|---|---|---|
| Logic Function | Octal bus transceiver with 3-state outputs | 3-to-8 line decoder/demultiplexer | Defines the core function; these devices are not functionally interchangeable as they perform entirely different logic operations. |
| Number of Channels / Outputs | 8 bidirectional channels | 8 decoded outputs (from 3 inputs) | Determines how many signals can be routed or controlled, affecting system architecture and pin count requirements. |
| Direction Control | Yes (DIR pin selects A-to-B or B-to-A) | No (unidirectional decoding only) | Bidirectional capability is essential for bus interfacing, while a decoder is inherently unidirectional. |
| Output Type | 3-state (tri-state) outputs | Active-low outputs (non-tri-state) | Tri-state outputs allow bus sharing; standard active-low outputs do not, impacting multi-device bus configurations. |
| Enable / Control Inputs | OE (output enable) and DIR | Three enable inputs (G1, G2A, G2B) | Control inputs determine how the device is gated or selected within a larger digital system. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both operate over the standard HC-family voltage range, allowing use in 3.3 V and 5 V logic systems. |
| Package | SO16 (SOIC-16) | SO16 (SOIC-16) | Identical package footprint means PCB layout compatibility, though pin functions differ. |
| Pin Count | 16 | 16 | Same pin count simplifies mechanical compatibility but does not imply electrical interchangeability. |
| Logic Family | HC (High-speed CMOS) | HC (High-speed CMOS) | Same logic family ensures compatible voltage thresholds and drive characteristics when interfacing with other HC devices. |
| Propagation Delay (typical at 5 V) | ~8 ns | ~14 ns | Timing differences affect maximum operating frequency and signal integrity in high-speed designs. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC238D | 74HC245D |
|---|---|---|
| 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 | 7.8mA, 7.8mA |
| Voltage Supply Source | Single Supply | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | - | Transceiver, Non-Inverting |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Output Type | - | 3-State |