Managing Electrical Parasitics and Capacitance in Extended Bus Sensor Harnesses
Managing sensor harness parasitics demands fluoropolymer dielectrics, matched line termination, active buffer acceleration, and strict shield grounding topology.
Logic Low Noise Margin
Noise Tolerance
Digital circuits require a specific voltage range to reliably distinguish a logic low state from a logic high state. The logic low noise margin is the difference between the maximum output voltage of a transmitter and the maximum input voltage a receiver will accept as low. This gap ensures that small amounts of noise on the signal line do not cause a false logic transition.
Voltage Threshold
Calculation of the logic low noise margin involves subtracting the output voltage from the input threshold. If a driver outputs a maximum of zero point four volts and the receiver accepts up to zero point eight volts, the margin is zero point four volts. A larger margin provides better immunity to crosstalk and ground bounce.
Component Selection
Designers optimize the logic low noise margin by selecting compatible logic families for the transmitter and receiver. Mixing different supply voltages often reduces this margin and requires level shifters to maintain reliability. Temperature changes affect the transistor switching points and can shrink the available noise floor.
Measurement of this parameter occurs during the characterization of the integrated circuit under worst case load conditions.
Reliability Metric
A robust logic low noise margin is necessary for systems operating in electromagnetically noisy industrial environments.