Can National Semiconductor\s LVDS receivers guarantee proper failsafe operation in extremely noisy environments?
The internal failsafe circuitry is designed to source/sink a very small amount of current, providing failsafe protection for floating inputs, shorted receiver inputs, and terminated receiver inputs as described in the components datasheet. It is not designed to provide failsafe in noisy environments such as when the cable is disconnected from the drivers end or if the driver is in tri-state. When this happens, the cable becomes a floating antenna that can pick up noise. If the cable picks up more noise than the internal failsafe circuitry can handle, the receiver may switch or oscillate. If this condition can happen in your application, it is recommended that you choose a balanced and/or shielded cable that will reduce the amount of differential noise on the cable. In addition, you may want to add external failsafe resistors to create a larger noise margin.
