Overview
The SN74HC21DRG4, produced by Texas Instruments, is a dual 4-input AND gate integrated circuit. This device is part of the 74HC series, known for its high-speed CMOS logic. It contains two independent 4-input AND gates, each performing the Boolean function Y = A ● B ● C ● D in positive logic. This component is widely used in digital logic circuits where multiple input signals need to be combined to produce a single output.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Supply Voltage (VCC) | 2 to 6 | V |
| Operating Temperature Range | -40 to 85 | °C |
| Input Clamp Current (IIK) | -20 to 20 | mA |
| Input Leakage Current (II) | ±0.1 to ±1 | µA |
| High-Level Output Voltage (VOH) | 1.9 to 5.9 | V |
| Low-Level Output Voltage (VOL) | 0.001 to 0.4 | V |
| Propagation Delay (tpd) | 11 to 140 | ns |
| Transition Time (tt) | 8 to 95 | ns |
| Input Capacitance (Ci) | 3 to 10 | pF |
| Supply Current (ICC) | 2 to 40 | µA |
| Junction-to-Ambient Thermal Resistance (RθJA) | 65.2 to 151.7 | °C/W |
Key Features
- Buffered inputs
- Wide operating voltage range: 2 V to 6 V
- Wide operating temperature range: -40°C to +85°C
- Supports fanout up to 10 LSTTL loads
- Significant power reduction compared to LSTTL logic ICs
- Balanced CMOS push-pull outputs
- Capable of driving larger currents than the device can sustain without damage, with proper output power limitation
Applications
The SN74HC21DRG4 is used in various digital logic applications where multiple input signals need to be combined. Some common applications include:
- Combining power good signals
- Enabling digital signals
- Controlling the RESET pin of a motor controller, where four input signals must all be HIGH before enabling the controller
- Implementing logic functions in digital circuits
Q & A
- What is the SN74HC21DRG4? The SN74HC21DRG4 is a dual 4-input AND gate integrated circuit produced by Texas Instruments.
- What is the Boolean function performed by each gate? Each gate performs the Boolean function Y = A ● B ● C ● D in positive logic.
- What is the operating voltage range of the SN74HC21DRG4? The operating voltage range is 2 V to 6 V.
- What is the operating temperature range of the SN74HC21DRG4? The operating temperature range is -40°C to +85°C.
- What is the maximum fanout for LSTTL loads? The device supports fanout up to 10 LSTTL loads.
- How does the SN74HC21DRG4 reduce power consumption compared to LSTTL logic ICs? The SN74HC21DRG4 has significant power reduction compared to LSTTL logic ICs due to its CMOS technology.
- What are the key features of the outputs of the SN74HC21DRG4? The outputs are balanced CMOS push-pull outputs capable of sinking and sourcing similar currents.
- How should unused inputs be handled? Unused inputs must be terminated to either VCC or ground, either directly or with a pull-up or pull-down resistor.
- What are the thermal considerations for the SN74HC21DRG4? The device has specified thermal metrics such as junction-to-ambient thermal resistance, and users must ensure the maximum junction temperature is not exceeded.
- What is the typical application of the SN74HC21DRG4 in motor control? It is used to control the RESET pin of a motor controller by combining four input signals into a single active-low reset signal.
