Solution
A TTL signal is a type of binary digital signal used in electronic circuits to represent an “off” or “on” state based on input and output voltages. A low voltage indicates “off” (logic 0) while a higher voltage indicates “on” (logic 1). Low voltage input signals are between 0 V and 0.8 V, and high voltage input signals are between 2 V and 5 V. The low voltage output signal is between 0 V and 0.4 V, while the high voltage output signal is between 2.4 V and 5 V.
A TTL signal must comply with the following specifications for the voltage and current output as well as for the voltage and current input. It must also comply with the pulse rise and fall time specification (rise/fall time), and the signal must have a minimum pulse width.
The specifications use the following notation:
- Output Low = OL
- Output High = OH
- Input Low = IL
- Input High = IH
1. Specifications for current and voltage output are as follows:
- V OL = 0.4V
- V OH = 2.4V
- I OL = 16mA
- I OH = 400µA
2. Specifications for current and voltage input are as follows
- V IL = 0.8V
- V IH = 2.0V
- I IL = 1.6mA
- I IH = 40µA
3. The maximum rise and fall time must be 50ns between high and low voltage.
4. The minimum width for different devices:
- Devices with NI-STC are 10ns.
- Devices with NI-TIO are 5ns.
