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參數(shù)資料
| 型號(hào)： | DS2119ME+T&R |
| 廠商： | Maxim Integrated Products |
| 文件頁(yè)數(shù)： | 2/9頁(yè) |
| 文件大?。?/td> | 0K |
| 描述： | IC TERM SCSI LVD/SE ULT3 28TSSOP |
| 產(chǎn)品培訓(xùn)模塊： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 標(biāo)準(zhǔn)包裝： | 2,500 |
| 類型： | SCSI，LVD，SE |
| 端子數(shù)： | 9 |
| 電源電壓： | 4 V ~ 5.5 V |
| 工作溫度： | 0°C ~ 70°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 28-TSSOP（0.173"，4.40mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 28-TSSOP |
| 包裝： | 帶卷 (TR) |
DS2119M
2 of 9
REFERENCE DOCUMENTS
Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface (SPI)
Project: 0855-M, 1995
Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface 2 (SPI-2) Project: 1142-M, 1998
Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface 3 (SPI-3) Project: 1302-D, 1999
Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface 4 (SPI-4) Project: 1365-D, 200x
Available From:
American National Standards Institute (ANSI) Phone: (212) 642-4900
Global Engineering Documents 15 Inverness Way East; Englewood, CO 80112 Phone: (800) 854-7179
FUNCTIONAL DESCRIPTION
The DS2119 combines LVD and SE termination with DIFFSENS sourcing and detection.
A bandgap reference is fed into two amplifiers, which creates a 1.25V reference voltage and a 2.85V
reference voltage. The control logic determines which of these references will be applied to the
termination resistors. If the SCSI bus is in LVD mode, then the 1.25V reference will be used. If the SCSI
bus is in SE mode, then the 2.85V reference will be used. That same control logic will switch in/out
parallel resistors to change the total termination resistance accordingly. Finally, in SE mode, the Rp pins
will be switched to ground.
The DIFFSENSE circuitry decodes trinary logic. There will be one of three voltages on the SCSI control
line called DIFFSENS. Two comparators and a NAND gate determine if the voltage is below 0.6V, above
2.15V, or in between. That indicates the mode of the bus to be SE, HVD, or LVD, respectively.
The DS2119M’s DIFF_CAP pin monitors the DIFFSENS line to determine the proper operating mode of
the device. The DIFFSENSE pin can also drive the SCSI DIFFSENS line (when MSTR/SLV = 1) to
determine the SCSI bus-operating mode. The DS2119M switches to the termination mode that is
appropriate for the bus based on the value of the DIFFSENS voltage. These modes are:
LVD Mode: LVD termination is provided by a precision laser-trimmed resistor string with two
current sources. This configuration yields a 105 differential and 150 common-mode
impedance. A fail-safe bias of 112mV is maintained when no drivers are connected to the SCSI
bus.
SE Mode: When the external driver for a given signal line turns off, the active terminator will pull
that signal line to 2.85V (quiescent state). When used with an active negation driver, the power
amp can sink 22mA per line and the reference voltage will move less than 100mV. The
terminating resistors maintain their 110
value.
HVD Isolation Mode: The DS2119M identifies that there is an HVD (high-voltage differential)
device on the SCSI bus and isolates the termination pins from the bus.
When ISO = 1, the termination pins are isolated from the SCSI bus, VREF remains active. During thermal
shutdown, the termination pins are isolated from the SCSI bus and VREF becomes high impedance. The
DIFFSENSE driver is shut down during either of these two events.
To ensure proper operation, the TPWR pin should be connected to the SCSI bus TERMPWR line. As
with all analog circuitry, the TERMPWR and VDD lines should be bypassed locally. A 2.2F capacitor
and a 0.01
F high-frequency capacitor are recommended between TPWR and ground and placed as close
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| DS211E | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Interface IC |
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| DS2120 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:Ultra3 LVD SCSI Terminator |
| DS2120B | 功能描述:SCSI 接口集成電路 RoHS:否 制造商:Texas Instruments 工作電源電壓:2.7 V to 5.25 V 電源電流:13 mA 最大工作溫度:+ 70 C 最小工作溫度:0 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SSOP-36 封裝:Tube |
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