Part A
74HC245D,653
NXP USA Inc.
- Lifecycle
- Active
- Stock
- 8186 Stückzahl
- Series
- Logic c Puffer, Treiber, Empfänger, Transceiver
Replacement verdict
Compatible functional replacement candidate
The 74HC244D and 74HC245D,653 are both octal non-inverting buffers from the 74HC family, sharing identical supply voltage, logic levels, and temperature ranges. However, the 74HC244D provides unidirectional buffering with dual active-low output enables, while the 74HC245D,653 offers bidirectional transceiver functionality with direction control and a single active-low output enable. This fundamental difference in data flow architecture means the 74HC245D,653 can serve as a functional replacement for the 74HC244D in unidirectional applications by tying the direction pin appropriately, but the reverse substitution requires careful validation of bidirectional requirements. Designers should verify pinout compatibility and control signal logic before committing to a drop-in replacement.
Function Type
Validation required
Supply Voltage
High match
Package Type
High match
Control Logic
Validation required
Parts at a glance
Part B
74HC244D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 7745 Stückzahl
- Package
- SOIC-20
- Series
- Logic c Puffer, Treiber, Empfänger, Transceiver
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC244D | 74HC245D,653 | Why it matters |
|---|---|---|---|
| Logic Function | Octal buffer/line driver with 3-state outputs, non-inverting, dual enable (1OE, 2OE) | Octal bus transceiver with 3-state outputs, non-inverting, direction control (DIR) and output enable (OE) | Determines whether the device can only buffer in one direction (244) or can transmit bidirectionally (245), which is critical for bus-oriented designs. |
| Direction Control | Unidirectional (fixed input-to-output) | Bidirectional via DIR pin | A bidirectional transceiver allows data flow in either direction, enabling use on shared buses; a unidirectional buffer cannot. |
| Number of Enable/Control Pins | 2 output enable pins (1OE, 2OE), each controlling 4 channels | 1 output enable (OE) and 1 direction (DIR) pin | Affects how the device is controlled in a system; the 244 allows split enabling of two 4-bit groups, while the 245 uses a single OE plus direction control. |
| Supply Voltage Range | 2.0 V to 6.0 V | 2.0 V to 6.0 V | Defines the compatible logic families and power rails; both support 2 V–6 V, making them interchangeable in many 3.3 V and 5 V systems. |
| Output Type | 3-state (tri-state) non-inverting | 3-state (tri-state) non-inverting | Tri-state outputs allow the device to be disconnected from a bus, which is essential for shared-bus architectures. |
| Number of Channels | 8 (octal) | 8 (octal) | Both provide eight buffered lines, so the channel count is not a differentiator for substitutability. |
| Package | SOIC-20 (D suffix) | SOIC-20 (D suffix) | Identical package and pin count simplify PCB layout and allow drop-in replacement considerations. |
| Propagation Delay (typical at 5 V) | ~11 ns | ~11 ns | Similar propagation delay means timing performance is comparable, so neither device introduces a significant speed penalty. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both cover the industrial temperature range, making them suitable for the same environmental conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC245D,653 | 74HC244D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Discontinued at DigiKey | Active |
| Base Product Number | 74HC245 | - |
| 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 | 7.8mA, 7.8mA | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C (TA) | -40°C ~ 85°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Packaging | Tape & Reel (TR) | - |
| Current - Output High Low | - | 7.8mA, 7.8mA |
Frequently asked questions
What is the main functional difference between the 74HC244D and the 74HC245D,653?
The 74HC244D is an octal non-inverting buffer/line driver with 3-state outputs, featuring a dual enable structure: it has two active-low output enable pins (1OE and 2OE), each controlling four outputs. The 74HC245D,653 is an octal bus transceiver with 3-state outputs, featuring a direction control pin (DIR) and a single active-low output enable pin (OE), allowing bidirectional data flow between two buses. In short, the 244 is a unidirectional buffer with two enable groups, while the 245 is a bidirectional transceiver with direction control.
Are the 74HC244D and 74HC245D,653 pin-compatible?
No. Although both are 20-pin devices in SOIC packages, their pin functions differ. The 74HC244D uses pins 1 and 19 as active-low output enables (1OE and 2OE), with all other pins being inputs or outputs in a fixed direction. The 74HC245D,653 uses pin 1 as DIR (direction control) and pin 19 as OE (active-low output enable), with pins 2–9 and 11–18 being bidirectional I/O ports (A1–A8 and B1–B8). Therefore, they are not pin-to-pin compatible and cannot be interchanged without circuit redesign.
Can the 74HC245D,653 replace the 74HC244D in a unidirectional buffering application?
Not directly. While the 74HC245D,653 can be configured for unidirectional data flow by setting the DIR pin to a fixed logic level, its pinout differs from the 74HC244D. The 244 has separate input and output pins for each channel, whereas the 245 has bidirectional I/O pins that serve as either input or output depending on DIR. This means the PCB layout and signal routing must be redesigned. Additionally, the 244 provides two independent enable groups, while the 245 has only one global enable, which may affect bus partitioning.
What are the key electrical specifications common to both the 74HC244D and 74HC245D,653?
Both devices are members of the 74HC logic family and share similar DC and AC characteristics when operated at the same supply voltage and temperature. Verified parameters from manufacturer datasheets include: wide supply voltage range of 2.0 V to 6.0 V, typical propagation delay of approximately 13 ns at 4.5 V, low input current of ±1 µA maximum, and 3-state outputs capable of driving up to ±6 mA at 4.5 V. Both are specified for operation over the –40 °C to +125 °C temperature range. For precise limits, always consult the specific manufacturer datasheet.
Which device is better suited for bidirectional bus applications?
The 74HC245D,653 is specifically designed for bidirectional bus applications. Its DIR pin allows data to flow from A to B or from B to A, making it ideal for microprocessor data buses, memory interfaces, and other bidirectional communication paths. The 74HC244D, being a unidirectional buffer, cannot perform bidirectional data transfer without external routing or additional logic. Therefore, for any application requiring two-way signal flow on the same bus, the 74HC245D,653 is the appropriate choice.
Do both devices have 3-state outputs?
Yes. Both the 74HC244D and the 74HC245D,653 feature 3-state outputs, which allow the outputs to be placed in a high-impedance state. This enables multiple devices to share a common bus without contention. On the 74HC244D, the 3-state condition is controlled by the two active-low output enable pins (1OE and 2OE). On the 74HC245D,653, the 3-state condition is controlled by the active-low output enable pin (OE), which disables both the A and B ports simultaneously.
What are the package and ordering differences between the 74HC244D and the 74HC245D,653?
The 74HC244D is typically supplied in a 20-pin SOIC package (SO20) by manufacturers such as Nexperia, with the "D" suffix indicating SOIC. The 74HC245D,653 is also a 20-pin SOIC device, but the ",653" suffix is a Nexperia ordering code indicating tape and reel packaging. Both devices are available in other package options from various manufacturers. When ordering, verify the full part number and packaging suffix to ensure the correct package and delivery format for your production requirements.
Can both devices operate at 3.3 V and 5 V logic levels?
Yes. Both the 74HC244D and the 74HC245D,653 are 74HC-family devices with a specified supply voltage range of 2.0 V to 6.0 V. This makes them compatible with both 3.3 V and 5 V logic systems. However, when interfacing between different voltage domains, ensure that the input voltage levels meet the VIH and VIL specifications for the given VCC, and that the outputs do not exceed the absolute maximum voltage ratings. Level shifting may be required if the driven device operates at a different supply voltage.