ds21t09 Maxim Integrated Products, Inc., ds21t09 Datasheet
ds21t09
Related parts for ds21t09
ds21t09 Summary of contents
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... The DS21T09 is intended for one-chip Plug and Play (PnP) SCSI termination. Plug and Play SCSI requires the exit-point terminator on computer motherboards or host bus adapters to automatically switch off if an external device is connected to the system. The DS21T09 satisfies this requirement by offering the engineer a choice of onboard current sensing circuitry or onboard ground detect circuitry external device is connected, the DS21T09 will automatically be isolated from the SCSI bus thereby maintaining proper system termination ...
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... CompuServe (Go plugplay). FUNCTIONAL DESCRIPTION The DS21T09 is designed single chip termination subsystem for use in PnP SCSI systems, Figure 1. When embedded on a host bus adapter or motherboard, the DS21T09 can automatically sense the termination status of the SCSI bus and attach or isolate its resistors as needed to maintain proper bus termination ...
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... When the Bus Ground Sensing Circuitry or Bus Current Sensing Circuitry determines that the SCSI bus is properly terminated without the DS21T09, the power-down buffer isolates the resistors from the SCSI bus and disables the power amp, thereby placing the DS21T09 in a low power mode (the bus sensing circuitry always stays active). The DS21T07 SCSI terminator for Wide SCSI configurations, Figure 8 ...
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... The power down capacitance on terminating resistors R1- R13 and R15-R18 is <3 pF; R14 is slightly higher due to the bus current sensing circuitry. The DS21T09 can be removed from the SCSI bus by using either of two automatic methods: Bus Ground Sensing or Bus Current Sensing. ...
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... BUS GROUND SENSING If internal and external SCSI devices are connected to the SCSI bus, the DS21T09 will disconnect from the SCSI bus according to the circuit in Figure 3. To utilize this automatic disconnect method of bus sensing, configure the DS21T09 as shown in Figure 4. The connected to pin 22 of the internal SCSI connector, and the pin 36 of the external SCSI connector ...
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... BUS CURRENT SENSING The DS21T09 has the capability to use current sensing to determine if the SCSI bus is over- or under- terminated =resistor in series with the SCSI bus (preferable the RST line) is used to monitor the bus current when that line pulls low (Active or “asserted” state). The resistor is between pad R14 and TCS on the die ...
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BUS CURRENT SENSE CONFIGURATION Figure 6 BUS CURRENT SENSE TIMING DIAGRAM Figure ...
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... NOTE: “1” denotes pin left open circuited. WIDE SCSI CONFIGURATION Figure 8 I > 32 mA? DS21T09 ISOLATED BUS FROM SCSI BUS Yes Yes Yes Yes Isolated Connected Connected Connected Isolated Isolated Isolated ...
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... Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. The Dallas Semiconductor DS21T09 is built to the highest quality standards and manufactured for long term reliability. All Dallas Semiconductor devices are made using the same quality materials and manufacturing methods ...
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NOTES TCS PDI PDE 2. 4.00V < TERMPWR < 5.50V. 3. 0.0V < signal lines < TERMPWR. 4. All signal lines = 0.0V. 5. All signal lines open. 6. Power down enabled. 7. Guaranteed by design; not ...