Part A
74AC245SCX
온세미
- Lifecycle
- Active
- Stock
- 5851 PCS
- Package
- SOIC-20
- Series
- 논리 - 버퍼, 드라이브, 수신기, 트랜시버
Replacement verdict
Compatible functional replacement candidate
The 74AC245SCX and 74AC244MTR are both 74AC-series octal buffers with identical supply voltage, logic family, and temperature ratings, but they differ in control architecture and pinout. The 74AC245SCX is a bidirectional transceiver with direction control, while the 74AC244MTR is a unidirectional non-inverting buffer with dual output enables. Direct substitution is possible only when the design does not require bidirectional data flow and the PCB footprint can accommodate the different pin assignments.
Logic Family
High match
Supply Voltage
High match
Output Type
Validation required
Pin Configuration
Not compatible
Parts at a glance
Part B
74AC244MTR
ST마이크로일렉트로닉스(주)
- Lifecycle
- Active
- Stock
- 3669 PCS
- Package
- SOIC-20
- Series
- 논리 - 버퍼, 드라이브, 수신기, 트랜시버
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74AC245SCX | 74AC244MTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Bus Transceiver (non-inverting, 3-state) | Octal Buffer/Line Driver (non-inverting, 3-state) | Determines the core function; a transceiver supports bidirectional data flow, while a buffer/driver is unidirectional, affecting whether the parts are functionally substitutable. |
| Direction Control | Direction pin (DIR) selects A-to-B or B-to-A | Two output-enable pins (1OE, 2OE), fixed A-to-Y direction | Bidirectional capability of the transceiver cannot be replicated by the unidirectional buffer, so pin-compatible replacement is not possible without redesign. |
| Number of Channels | 8 | 8 | Matching channel count ensures equivalent bus width handling for parallel data lines. |
| Output Type | 3-state | 3-state | 3-state outputs allow multiple devices to share a common bus without contention. |
| Logic Family | AC (Advanced CMOS) | AC (Advanced CMOS) | Same logic family ensures compatible input thresholds, output drive, and switching characteristics. |
| Supply Voltage Range | 2.0 V to 6.0 V | 2.0 V to 6.0 V | Compatible operating voltage range allows use in the same power supply environment. |
| Output Drive Current | ±24 mA | ±24 mA | Matching drive strength ensures similar fan-out and signal integrity performance. |
| Propagation Delay | ~5.5 ns at 5 V | ~5.5 ns at 5 V | Similar propagation delay preserves timing margins in synchronous systems. |
| Package Type | SOIC-20 (SOP-20) | SOIC-20 (SOP-20) | Package footprint affects PCB layout; both share SOIC-20 but pinouts differ due to function, so direct drop-in is not possible. |
| Pin Configuration | DIR and OE control pins; A and B ports | 1OE and 2OE control pins; A inputs and Y outputs | Different pin functions and control logic prevent direct pin-to-pin substitution despite identical package size. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74AC245SCX | 74AC244MTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74AC | 74AC |
| Part Status | Active | Obsolete |
| Logic Type | Transceiver, Non-Inverting | Buffer, Non-Inverting |
| Number of Elements | 1 | 2 |
| Number of Bits per Element | 8 | 4 |
| Output Type | 3-State | 3-State |
| Current - Output High Low | 24mA, 24mA | 24mA, 24mA |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C (TA) | -55°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary functional differences between the 74AC245SCX and the 74AC244MTR?
The 74AC245SCX is an octal bus transceiver with non-inverting 3-state outputs, designed for bidirectional asynchronous communication between data buses. The 74AC244MTR is an octal buffer/line driver with non-inverting 3-state outputs, intended for unidirectional signal buffering. The 74AC245SCX provides direction control (DIR) and output enable (OE), while the 74AC244MTR provides two separate output enable pins (1OE and 2OE) for independent control of two 4-bit groups.
Are the 74AC245SCX and 74AC244MTR pin-to-pin compatible?
No. The 74AC245SCX and 74AC244MTR have different pinouts. The 74AC245SCX uses a bidirectional transceiver pinout with A-side and B-side ports, a direction pin (DIR), and an output enable pin (OE). The 74AC244MTR uses a unidirectional buffer pinout with separate input and output pins arranged in two 4-bit sections, each with its own output enable. They are not direct drop-in replacements.
Can the 74AC245SCX be used as a direct substitute for the 74AC244MTR in an existing design?
No, not as a direct substitute. Although both are 74AC-series octal devices with 3-state outputs, the 74AC245SCX is a bidirectional transceiver and the 74AC244MTR is a unidirectional buffer. Pinouts, control logic, and signal flow differ. Substitution requires redesign of the PCB layout and verification of control signal timing against the manufacturer datasheets.
What are the package types for the 74AC245SCX and 74AC244MTR?
The 74AC245SCX is supplied in a 20-pin SOIC package (SC suffix indicates SOIC). The 74AC244MTR is supplied in a 20-pin SOIC package (MTR suffix indicates tape and reel, SOIC). Both are surface-mount 20-pin SOIC packages, but their pin assignments differ as noted above.
Do both devices operate at the same supply voltage and logic levels?
Yes. Both the 74AC245SCX and 74AC244MTR are AC-series CMOS devices typically specified for a supply voltage range of 2.0 V to 6.0 V, with characterized operation at 5.0 V. They provide CMOS-compatible inputs and can drive both CMOS and TTL loads within the specified fan-out and current limits. Always confirm exact VCC range and input/output thresholds from the specific manufacturer datasheet.
What is the difference in control pins between the 74AC245SCX and the 74AC244MTR?
The 74AC245SCX has two control pins: DIR (direction) and OE (output enable). DIR selects whether data flows from A to B or B to A. OE disables both ports to high-impedance when inactive. The 74AC244MTR has two output enable pins, 1OE and 2OE, each controlling one 4-bit group of outputs. There is no direction control because the 74AC244MTR is unidirectional.
Which device is better for bidirectional bus applications?
The 74AC245SCX is intended for bidirectional bus applications because it integrates direction control and can drive either side of a bus. The 74AC244MTR is intended for unidirectional buffering and cannot reverse signal flow. For bidirectional data buses, the 74AC245SCX is the appropriate choice when used within its specified operating conditions.
Are the output drive currents the same for the 74AC245SCX and 74AC244MTR?
Both devices are in the 74AC logic family and typically provide symmetrical output drive of ±24 mA at 5.0 V VCC, as specified in standard AC-series datasheets. However, actual drive current can vary by manufacturer and test conditions. Always verify the IOH and IOL ratings from the specific manufacturer datasheet for the exact part number and package.