termination resistor for driver

Question

In the datasheet, the most of DRIVER ac specifications have comment "terminated", except Rise/Fall time for 4V programmed swing. 
 Usually, do we need to add the 50&Omega; termination resistor in the actual DUT? 
 what will happen if I won't add the termination resistor? will the reflection affect on the waveform?

mench · Accepted Answer

Hi ogura.isao@sankyosha.co.jp , 
 
 To answer your first question: It depends on what logic family you are using. When you are dealing with high-speed signals (logic families such as LVDS, CML, ECL, PECL, etc.) they are typically 50 ohm terminated applications but if you are working in low-speed applications (older logic families like 5V TTL, 3.3 V CMOS) they are typically unterminated. 
 
 You may check out these notes on AnalogDialogue that may help with some basics on interfacing high-speed signals. 
 
 Interfacing High-Speed Signals | Analog Devices 
 Propagation Delay Measurements Using TDR (Time-Domain Reflectometry) | Analog Devices 
 
 To answer your second question: If you're using high speed logic families, yes, the reflection will affect the waveform if driving an unterminated load. If you're working on low speed it rarely causes any problem. 
 
 Best regards, 
 Menchie)

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termination resistor for driver