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LX5111A Datasheet(PDF) 4 Page - Microsemi Corporation |
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LX5111A Datasheet(HTML) 4 Page - Microsemi Corporation |
4 / 4 page UL TRA 9-C HANNEL SCSI T ERMINA T O R LX5111A/5112A PRODUCT DA T ABOOK 1996/1997 Copyright © 1999 Rev. 0.1 3/99 4 P RELIMINAR Y D AT A S HEET UltraMAX BLOCK DIAGRAM FUNCTIONAL DESCRIPTION TERM POWER CURRENT BIASING CIRCUIT 1.4V DISCONNECT (5111) DISCONNECT (5112) 24mA CURRENT LIMITING CIRCUIT DATA OUTPUT PIN DB(0) 2.85V 1 OF 9 CHANNELS Cable transmission theory suggests to optimize signal speed and quality, the termination should act both as an ideal voltage reference when the line is released (deasserted) and as an ideal current source when the line is active (asserted). Common active terminators, which consist of Linear Regulators in series with resistors (typically 110 Ω), are a compromise. As the line voltage increases, the amount of current decreases linearly by the equation V = I * R. The LX5111A/5112A, with their unique new architecture ap- plies the maximum amount of current regardless of line voltage until the termination high threshold (2.85V) is reached. Acting as a near ideal line terminators, the LX5111A/5112A closely reproduce the optimum case when the devices are enabled. To enable the device the DISCONNECT pin (DISCONNECT pin for the LX5112A) must be pulled logic High (logic Low for the LX5112A). During this mode of operation, quiescent current is 6mA and the devices will respond to line demands by delivering 24mA on assertion, and by imposing 2.85V on deassertion. In order to disable the device, the DISCONNECT pin (DISCONNECT pin for the LX5112A) must be driven logic Low (logic High for the LX5112A). This mode of operation places the devices in a sleep state where a meager 275µA of quiescent current is con- sumed. Additionally, all outputs are in a Hi-Z (impedance) state. Sleep mode can be used for power con- servation or to completely eliminate the terminator from the SCSI chain. In the second case, termination node capacitance is important to consider. The terminators will ap- pear as a parasitic distributed capaci- tance on the line, which can detract from bus performance. For this reason, the LX5111A/5112A have been optimized to have only 3pF of capacitance per output in the sleep state. An additional feature of the LX5111A/5112A IC's are their compatibility with active negation drivers. UltraMAX is a trademark of Linfinity Microelectronics Inc. Outputs Quiescent Current H L Enabled 6mA L H HI Z 275µA Open Open HI Z 275µA LX5111A LX5112A DISCONNECT DISCONNECT POWER UP / POWER DOWN FUNCTION TABLE PRELIMINARY DATA - Information contained in this document is pre-production data, and is proprietary to LinFinity. It may not modified in any way without the express written consent of LinFinity. Product referred to herein is offered in sample form only, and Linfinity reserves the right to change or discontinue this proposed product at any time. |
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