Electronic digital logic circuitry – Signal sensitivity or transmission integrity – Bus or line termination
Patent
1995-03-23
1996-08-13
Westin, Edward P.
Electronic digital logic circuitry
Signal sensitivity or transmission integrity
Bus or line termination
327310, 333 22R, H03K 190185
Patent
active
055460178
ABSTRACT:
The invention is an active, hot insertable, SCSI terminator circuit having a bypass device that permits an initially unpowered active SCSI terminator to be coupled to a signal line of a powered SCSI bus such that no damage results to the SCSI terminator circuit itself or to other SCSI devices on the SCSI bus, and without having the effect of altering the existing state of the SCSI bus as a result of the coupling. Preferably, the terminating element of the SCSI terminator is a p-channel MOSFET. The SCSI terminator is prevented from being damaged during the coupling by using the bypass device to effectively short the gate of the p-channel MOSFET terminating element to its drain. When the drain of the p-channel MOSFET terminating element is shorted to its gate the amount of current the SCSI terminator may draw from any and all SCSI signal lines during the coupling is substantially limited to less than 50 .mu.A. The bypass device performs the shorting function until a SCSI terminator reference voltage powers up to its steady state value, after which the bypass device is disabled.
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Westin Edward P.
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