Overview
The SN74HCS21DR, produced by Texas Instruments, is a dual 4-input AND gate with Schmitt-trigger inputs. This device is part of the HCS (High-Speed CMOS) logic family and is designed to operate over a wide voltage range from 2 V to 6 V. It features two independent AND gates, each performing the Boolean function Y = A ● B ● C ● D in positive logic. The Schmitt-trigger inputs enhance the device's ability to handle slow or noisy input signals, making it suitable for various digital logic applications.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Supply Voltage (VCC) | 2 | - | 6 | V |
| Input Voltage (VI) | 0 | - | VCC | V |
| Ambient Temperature (TA) | -40 | - | 125 | °C |
| Supply Current (ICC) | - | 0.1 | 2 | µA |
| Input Capacitance (Ci) | - | - | 5 | pF |
| Output Drive Current | - | - | ±7.8 | mA |
| Junction-to-Ambient Thermal Resistance (RθJA) | - | - | 151.7 (TSSOP), 133.6 (SOIC) | °C/W |
Key Features
- Wide Operating Voltage Range: The device operates from 2 V to 6 V, making it versatile for various applications.
- Schmitt-Trigger Inputs: Allows for slow or noisy input signals and provides noise rejection.
- Low Power Consumption: Typical supply current of 100 nA and typical input leakage current of ±100 nA.
- High Output Drive Capability: ±7.8-mA output drive at 5 V.
- Extended Ambient Temperature Range: Operates from -40°C to +125°C.
- Balanced CMOS Push-Pull Outputs: Outputs can sink and source similar currents, ensuring balanced performance.
Applications
- Combining Power Good Signals: The device can be used to combine multiple power good signals into a single output.
- Enable Digital Signals: It can be used to enable or disable digital signals based on multiple input conditions.
- System Reset Control: The SN74HCS21 can drive the RESET pin of a system controller, ensuring the controller operates only when all inputs are in a valid state.
Q & A
- What is the operating voltage range of the SN74HCS21DR?
The SN74HCS21DR operates over a voltage range from 2 V to 6 V.
- What is the purpose of Schmitt-trigger inputs in the SN74HCS21DR?
Schmitt-trigger inputs allow the device to handle slow or noisy input signals and provide noise rejection.
- What is the typical supply current of the SN74HCS21DR?
The typical supply current (ICC) is 0.1 µA.
- What is the output drive capability of the SN74HCS21DR at 5 V?
The output drive capability is ±7.8 mA at 5 V.
- What is the ambient temperature range for the SN74HCS21DR?
The device operates from -40°C to +125°C.
- Can the SN74HCS21DR be used in safety-critical applications?
No, it is not recommended for use in safety-critical applications without thorough validation and testing.
- How many AND gates are included in the SN74HCS21DR?
The device includes two independent 4-input AND gates.
- What is the junction-to-ambient thermal resistance for the SOIC package?
The junction-to-ambient thermal resistance (RθJA) for the SOIC package is 133.6 °C/W.
- Can the outputs of the SN74HCS21DR be left floating?
Yes, unused outputs can be left floating.
- What is the recommended capacitive load for optimal performance?
The capacitive load at the output should be less than or equal to 70 pF for optimal performance.
