The termination resistance of RS485 depends on the transmission line being used. It is equal to the characteristic impedance of the transmission line, which is typically 110 - 130 Ohm. Whether termination is required depends on the data transmission rate, cable length, and slew rate. RS485 transceivers are typically connected to UART, which samples data at the midpoint of every data bit. As long as the reflected signal is attenuated to a sufficiently low level at the start of sampling, no matching may be required. The following empirical guideline may be used to determine at which data rate and cable length matching is needed: When the signal rise and fall time is slower than 3 times the propagation delay, no matching is required.
Learn
Libraries
Upcoming Learning & Events
- Power Integrity: LDOs for AI Infrastructure, Edge & Robotics
- The Missing Middle in AESA Development: From Beamforming ICs to Scalable Apertures
- Motor Drive Fundamentals Session 3: Safe Torque Off Architectures and Claiming Fault Exclusion
- Motor Drive Fundamentals Session 2: Designing for EMC Success in Modern Motor Control Systems
- New Lowest-Power ZIF-Based SDR Transceivers for RF Instrumentation and Defense Applications
- View All Webinars
Community Hub
Resources
Challenge Yourself
KCC's Quizzes AQQ305 about a mutual exponentiation equation
1. Quote of the month: "A train station is where a train stops. A bus station is where a bus stops. I have a work station on my desk, so..." - unknown
2. Quiz AQQ305 about finding a mutual exponential equation
Good luck, and try to be among the
View All
What's Brewing
September Monthly Blog Quiz! Read the blog, take the quiz, and you could win a gift card
Quiz: How Well Do You Know Adaptive Power Switching?
Is your I/O module overheating? The AD74416H's Adaptive Power Switching (APS) can cut heat dissipation by up to 40% — but how well do you really understand how it works?
Read the blog first: Cooling
View All