SFFS138 December   2021 TCAN1164-Q1

 

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5.3.1.3 SM-3: CAN bus short circuit limiter, IOS

These devices limit the short-circuit current when a CAN bus line is shorted. The CAN driver is current limited (dominant and recessive) with values of ± 115 mA for IOS_DOM and ± 5 mA for IOS_REC. During CAN communication the bus switches between dominant and recessive states; thus, the short-circuit current may be viewed either as the current during each bus state or as a DC average current. For system current and power considerations in the termination resistors and common mode choke ratings, the average short-circuit current should be used. The percentage dominant is limited by the TXD dominant time out and CAN protocol which has forced state changes and recessive bits such as bit stuffing, control fields, and inter frame space. These ensure there is a minimum recessive amount of time on the bus even if the data field contains a high percentage of dominant bits. See data sheet for more information.