Part A
74HC238D
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 5394 PCS
- Package
- SOIC-16
- Series
- Logic - Signal Switches, Multiplexers, Decoders
Replacement verdict
Not a drop-in replacement
The 74HC238D and 74HC245D,652 are functionally unrelated logic ICs and cannot serve as substitutes for one another. The 74HC238D is a 3-to-8 line decoder/demultiplexer with eight mutually exclusive active-low outputs, while the 74HC245D,652 is an octal bidirectional transceiver with dual-direction bus control. Their internal architectures, pin functions, and control logic differ fundamentally, so neither device can directly replace the other in an existing design without significant circuit redesign.
Different logic function
Different output type
Different channel count
Different control interface
Parts at a glance
Part B
74HC245D,652
NXP Hoa Kỳ Inc.
- Lifecycle
- Active
- Stock
- 4100 PCS
- Package
- SOIC-20
- Series
- Logic - 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 | 74HC238D | 74HC245D,652 | Why it matters |
|---|---|---|---|
| Logic Function | 3-to-8 line decoder/demultiplexer | Octal bus transceiver with 3-state outputs | The core function determines whether the device can be substituted at all; a decoder and a bus transceiver serve fundamentally different roles in a circuit. |
| Number of Channels / Outputs | 8 outputs (one of eight decoded) | 8 bidirectional channels | Channel count and directionality affect how many signals can be routed and whether data can flow both ways. |
| Directionality | Unidirectional (inputs to decoded outputs) | Bidirectional (A-to-B or B-to-A controlled by DIR) | Bidirectional capability is essential for bus interfacing, while a decoder is strictly unidirectional. |
| Output Type | Active-low decoded outputs (non-3-state) | 3-state outputs | 3-state outputs allow bus sharing by high-impedance disconnection, which the decoder cannot provide. |
| Control Inputs | 3 address inputs plus 3 enable inputs (two active-low, one active-high) | Direction (DIR) and Output Enable (OE) inputs | Control pin configuration determines how the device is driven and whether it fits the intended logic scheme. |
| Supply Voltage Range | 2.0 V to 6.0 V | 2.0 V to 6.0 V | Matching supply voltage ranges ensures compatibility with the target system's power rail. |
| Logic Family | HC (High-speed CMOS) | HC (High-speed CMOS) | Same logic family implies compatible input thresholds, noise margins, and drive characteristics. |
| Package | SO16 (SOIC-16) | SO20 (SOIC-20) | Different package footprints and pin counts prevent direct drop-in replacement on the same PCB pad layout. |
| Pin Count | 16 pins | 20 pins | Pin count mismatch means the devices are not pin-compatible and cannot share the same socket. |
| Typical Propagation Delay | Approximately 14 ns at 4.5 V | Approximately 8 ns at 4.5 V | Propagation delay affects timing margins in high-speed digital systems and can impact signal integrity. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC238D | 74HC245D,652 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | - | Transceiver, Non-Inverting |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Output Type | - | 3-State |
| Current - Output High Low | 5.2mA, 5.2mA | 7.8mA, 7.8mA |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Type | Decoder/Demultiplexer | - |
| Circuit | 1 x 3:8 | - |
| Independent Circuits | 1 | - |
| Voltage Supply Source | Single Supply | - |