Overview
The SN74HC20DRG4, produced by Texas Instruments, is a dual 4-input NAND gate integrated circuit. This device is part of the 74HC series, known for its high-speed CMOS logic and wide operating voltage range. Each gate within the SN74HC20 performs the Boolean function Y = A ● B ● C ● D in positive logic, making it versatile for various digital logic applications.
Key Specifications
| Parameter | Condition | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| VCC Supply Voltage | -0.5 | 7 | V | ||
| Operating Free-Air Temperature (TA) | -40 | 85 | °C | ||
| High-Level Output Voltage (VOH) | VCC = 4.5 V, IOH = -20 µA | 4.4 | 4.499 | 4.4 | V |
| Low-Level Output Voltage (VOL) | VCC = 4.5 V, IOL = 20 µA | 0.001 | 0.1 | 0.1 | V |
| Propagation Delay (tpd) | CL = 50 pF, VCC = 4.5 V | 9 | 22 | 28 | ns |
| Transition Time (tt) | CL = 50 pF, VCC = 4.5 V | 9 | 15 | 19 | ns |
| Power Dissipation Capacitance per Gate | No load, 2 V to 6 V | 25 | pF |
Key Features
- Buffered Inputs: Ensures stable and reliable input signals.
- Wide Operating Voltage Range: Operates from 2 V to 6 V, making it versatile for different system designs.
- Wide Operating Temperature Range: Functional from -40°C to +85°C, suitable for various environmental conditions.
- High Fanout Capability: Supports up to 10 LSTTL loads.
- Low Power Consumption: Significant power reduction compared to LSTTL logic ICs.
- Balanced CMOS Push-Pull Outputs: Allows the device to sink and source similar currents.
- Clamp Diode Structure: Inputs and outputs have both positive and negative clamping diodes for protection.
Applications
- Alarm and Tamper Detect Circuits: Can be used to drive tamper indicator LEDs and provide data to system controllers.
- S-R Latches: Two 4-input NAND gates can be configured to create active-low SR latches.
- General Digital Logic Circuits: Suitable for various digital logic applications requiring 4-input NAND gates.
Q & A
- What is the primary function of the SN74HC20DRG4?
The SN74HC20DRG4 contains two independent 4-input NAND gates, each performing the Boolean function Y = A ● B ● C ● D in positive logic.
- What is the operating voltage range of the SN74HC20DRG4?
The device operates from 2 V to 6 V.
- What is the operating temperature range of the SN74HC20DRG4?
The device is functional from -40°C to +85°C.
- How many LSTTL loads can the SN74HC20DRG4 support?
The device supports up to 10 LSTTL loads.
- What is the significance of the clamp diode structure in the SN74HC20DRG4?
The inputs and outputs have both positive and negative clamping diodes, which provide protection against voltage spikes.
- Can the SN74HC20DRG4 be used to create an S-R latch?
Yes, two 4-input NAND gates can be configured to create an active-low SR latch.
- How should unused inputs be handled in the SN74HC20DRG4?
Unused inputs must be terminated to either VCC or ground, either directly or with pull-up or pull-down resistors.
- What are the recommendations for output considerations?
The positive supply voltage produces the output HIGH voltage, and drawing current from the output decreases the output voltage. Similarly, sinking current into the output increases the output voltage.
- What is the typical propagation delay for the SN74HC20DRG4?
The propagation delay (tpd) is typically around 22 ns for VCC = 4.5 V and CL = 50 pF.
- How should the power supply be managed for the SN74HC20DRG4?
Ensure the supply voltage is within the specified range, and the supply must be capable of sourcing current equal to the total current required by all outputs plus the maximum supply current.
