Hot-switchable SCSI controller having output drivers with quick turn-on
First Claim
1. An integrated circuit including an output driver coupled to a terminated SCSI bus, the output driver having a quick turn-on characteristic and configured to be hot-switchable onto and off of an active SCSI bus, the integrated circuit comprising:
- an output driver including an N-channel pull-up transistor and an N-channel pull-down transistor, the pull-up transistor having a turn-on characteristic in operative response to a charge current magnitude provided on a gate terminal thereof;
a resistor divider network coupled to the gate terminal, the resistor divider network including a resistor coupled in series with the charge current path and a resistor coupled in parallel to the charge current path;
bypass means coupled in parallel with series resistor; and
feedback means coupled between an output of said output driver and the bypass means, the feedback means in operative response to an output voltage of said output driver output, the feedback means configured in a first state when said output voltage is below a trigger value, the feedback means first state for maintaining feedback means in an on condition thereby bypassing said series resistor, the feedback means configured in a second state said output voltage is above a trigger value, said feedback means second state turning off said bypass means thereby allowing current flow through said series resistor.
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Accused Products
Abstract
An integrated circuit provides for an output driver having a quick turn-on characteristic as well as a maximum VOH level limited to the maximum SCSI specification limit. The output driver'"'"'s VOH is controlled by a resistor divider network, connected between a pull-up signal source and a pull-up output device, and which functions to reduce the gate voltage on the output device such that its maximum VOH level is limited to the SCSI specification. The quick turn-on characteristic is implemented by coupling a transfer gate in parallel with the series resistor of the resistor divider network, and bypassing the series resistor during a first portion of the pull-up turn-on time of the output driver. A feedback circuit is connected between the output driver output and the transfer gate bypass circuit, in order to turn the transfer gate off when the output voltage reaches a particular trigger value, thus removing the bypass from the series resistor and allowing the resistor divider network to function normally and limit the output driver'"'"'s pull-up to the maximum SCSI VOH limit. The transfer gate is further configured to allow an SCSI device incorporating the circuit to be hot-switched onto and off of an active SCSI bus.
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Citations
23 Claims
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1. An integrated circuit including an output driver coupled to a terminated SCSI bus, the output driver having a quick turn-on characteristic and configured to be hot-switchable onto and off of an active SCSI bus, the integrated circuit comprising:
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an output driver including an N-channel pull-up transistor and an N-channel pull-down transistor, the pull-up transistor having a turn-on characteristic in operative response to a charge current magnitude provided on a gate terminal thereof; a resistor divider network coupled to the gate terminal, the resistor divider network including a resistor coupled in series with the charge current path and a resistor coupled in parallel to the charge current path; bypass means coupled in parallel with series resistor; and feedback means coupled between an output of said output driver and the bypass means, the feedback means in operative response to an output voltage of said output driver output, the feedback means configured in a first state when said output voltage is below a trigger value, the feedback means first state for maintaining feedback means in an on condition thereby bypassing said series resistor, the feedback means configured in a second state said output voltage is above a trigger value, said feedback means second state turning off said bypass means thereby allowing current flow through said series resistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An integrated circuit for adaptively switching an output driver coupled to a terminated SCSI bus between a first, quick turn-on mode and a second, VOH limiting mode, the integrated circuit comprising:
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an output driver including an N-channel pull-up transistor and an N-channel pull-down transistor, the pull-up transistor having a turn-on characteristic in operative response to a charge current magnitude provided on a gate terminal thereof, the pull-up transistor further having a maximum VOH characteristic in operative response to a control voltage magnitude provided on said gate terminal; a control voltage limiting circuit coupled between the gate terminal of the pull-up transistor and a control voltage signal source; a charge current bypass circuit coupled between the gate terminal of the pull-up transistor and the control voltage signal source, the bypass circuit further connected in parallel with the control voltage limiting circuit; and feedback means coupled between an output of the output driver and the charge current bypass circuit, the feedback means in operative response to an output voltage of the output driver such that when the output voltage is below a trigger value, the feedback means activates the charge current bypass circuit, thereby providing a direct charge current path between the signal source and the gate terminal of the pull-up transistor, and when the output voltage is above the trigger value, the feedback means deactivates the bypass circuit thereby placing the control voltage limiting means in the charge current path between the signal source and the gate terminal of the pull-up transistor. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. An integrated circuit for adaptively switching an output driver coupled to a terminated SCSI bus between a first, quick turn-on mode and a second, VOH limiting mode, the integrated circuit comprising:
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an output driver including an N-channel pull-up transistor and an N-channel pull-down transistor, the pull-up transistor having a turn-on characteristic in operative response to a charge current magnitude provided on a gate terminal thereof, the pull-up transistor further having a maximum VOH characteristic in operative response to a control voltage magnitude provided on said gate terminal; a control voltage limiting circuit coupled between the gate terminal of the pull-up transistor and a control voltage signal source; a charge current bypass circuit coupled between the gate terminal of the pull-up transistor and the control voltage signal source, the bypass circuit further connected in parallel with the control voltage limiting circuit; feedback means coupled between an output of the output driver and the charge current bypass circuit, the feedback means in operative response to an output voltage of the output driver such that when the output voltage is below a trigger value, the feedback means activates the charge current bypass circuit, thereby providing a direct charge current path between the signal source and the gate terminal of the pull-up transistor, and when the output voltage is above the trigger value, the feedback means deactivates the bypass circuit thereby placing the control voltage limiting means in the charge current path between the signal source and the gate terminal of the pull-up transistor; and a hot-switch circuit, operatively coupled to a reset signal, for placing the N-channel pull-up and N-channel pull-down transistors into tri-state in response to reset being in a first logical state, the hot-switch circuit releasing the N-channel pull-up and N-channel pull-down transistors from tri-state in response to reset being in a second logical state. - View Dependent Claims (22, 23)
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Specification