Part A
74HC244D
Компания Toshiba Semiconductor и Storage
- Lifecycle
- Active
- Stock
- 7745 ПКС
- Package
- SOIC-20
- Series
- Логика - буферы, драйверы, приемники, передатчики
Replacement verdict
Not a drop-in replacement
The 74HC244D and 74HC21D,653 are not functionally interchangeable. The 74HC244D is an octal non-inverting buffer/line driver with 3-state outputs, while the 74HC21D,653 is a dual 4-input AND gate. Their logic functions, channel configurations, output structures, and pin assignments are fundamentally different, making direct substitution impossible without complete circuit redesign.
Different logic function
Different channel count
Different output type
Different pinout
Parts at a glance
Part B
74HC21D,653
Компания NXP Semiconductors
- Lifecycle
- Active
- Stock
- 8890 ПКС
- Series
- Логика - Ворота и инверторы
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 | 74HC21D,653 | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver with 3-state outputs | Dual 4-input AND gate | The core logic function determines whether the parts are functionally interchangeable; these devices perform entirely different operations. |
| Number of Gates/Channels | 8 buffers (2 groups of 4) | 2 AND gates | Channel count affects how many signals can be processed and the physical fit in a given circuit design. |
| Output Type | 3-state (tri-state) outputs | Push-pull (totem-pole) outputs | Tri-state outputs allow bus sharing and high-impedance disconnection, while push-pull outputs cannot be tied together. |
| Number of Inputs per Element | 1 input per buffer | 4 inputs per gate | Input count per element defines the logic complexity each element can handle. |
| Propagation Delay (typical at 5V) | ~13 ns | ~15 ns | Propagation delay affects maximum operating frequency and timing margins in synchronous designs. |
| Output Drive Current (IOH/IOL) | ±6 mA (standard HC drive) | ±4 mA (standard HC drive) | Drive current determines the ability to drive loads such as LEDs, other logic inputs, or transmission lines. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | The supply voltage range must match the system power rail for proper operation and logic level compatibility. |
| Package Type | SOIC-20 (D suffix) | SOIC-14 (D suffix) | Package footprint and pin count must match the PCB layout for physical compatibility. |
| Pin Count | 20 pins | 14 pins | Pin count determines the physical footprint and the number of connections available on the PCB. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +125°C | The temperature range must cover the application environment to ensure reliable operation. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC244D | 74HC21D,653 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Part Status | Active | Active |
| Series | 74HC | - |
| Logic Type | Buffer, Non-Inverting | - |
| Number of Elements | 2 | - |
| Number of Bits per Element | 4 | - |
| Output Type | 3-State | - |
| Current - Output High Low | 7.8mA, 7.8mA | - |
| Voltage - Supply | 2V ~ 6V | - |
| Operating Temperature | -40°C ~ 85°C (TA) | - |
| Mounting Type | Surface Mount | - |
Frequently asked questions
What are the primary functional differences between the 74HC244D and the 74HC21D,653?
The 74HC244D is an octal non-inverting buffer/line driver with 3-state outputs, while the 74HC21D,653 is a dual 4-input AND gate. They perform fundamentally different logic functions and are not functionally interchangeable.
Do the 74HC244D and 74HC21D,653 share the same package type?
Both devices are typically offered in SOIC packages. The 74HC244D is commonly supplied in a 20-pin SOIC package, while the 74HC21D,653 is supplied in a 14-pin SOIC package. Package pin counts and PCB land patterns differ, so they are not drop-in compatible.
Can the 74HC244D and 74HC21D,653 operate from the same supply voltage range?
Yes. Both are 74HC-series CMOS devices and are specified for a nominal supply voltage range of 2.0 V to 6.0 V, with 5 V being the most common operating condition.
What is the output drive capability of the 74HC244D compared with the 74HC21D,653?
The 74HC244D is specified with standard 74HC output drive, typically ±6 mA at 5 V, and includes 3-state outputs for bus-oriented applications. The 74HC21D,653 provides standard 74HC logic gate outputs, typically ±4 mA at 5 V, and does not have 3-state outputs.
Are the 74HC244D and 74HC21D,653 pin-compatible?
No. The 74HC244D uses a 20-pin configuration with eight buffer channels, output enable pins, and multiple ground and supply pins. The 74HC21D,653 uses a 14-pin configuration with two 4-input AND gates. Pin counts, pin functions, and pinouts are different.
Which device is suitable for driving a shared data bus?
The 74HC244D is suitable for shared data bus applications because it provides 3-state outputs that can be placed in a high-impedance state. The 74HC21D,653 is a logic gate and does not provide 3-state outputs, so it is not intended for direct bus driving.
Can the 74HC244D and 74HC21D,653 be used in the same design?
Yes, they can be used together in the same design because they perform different functions. The 74HC244D can buffer or drive signals, while the 74HC21D,653 can implement a 4-input AND logic function. They are complementary rather than substitutes.
Do both devices have the same operating temperature range?
Both are typically specified for the standard 74HC industrial temperature range of -40 °C to +125 °C, but the exact rating should always be confirmed from the specific manufacturer datasheet for the ordered part number.