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參數(shù)資料
| 型號(hào)： | DS21T09S |
| 廠商： | DALLAS SEMICONDUCTOR |
| 元件分類： | Bus Terminator |
| 英文描述： | 18-LINE 110 ohm SCSI BUS TERMINATOR, PDSO28 |
| 封裝： | 0.300 INCH, SOIC-28 |
| 文件頁(yè)數(shù)： | 7/10頁(yè) |
| 文件大?。?/td> | 221K |
| 代理商： | DS21T09S |
DS21T09
6 of 10
BUS CURRENT SENSING
The DS21T09 has the capability to use current sensing to determine if the SCSI bus is over- or under-
terminated. A 1
=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. Based on the current measured, the DS21T09 will disconnect or connect from the SCSI bus. The
configuration for this automatic isolation technique is shown in Figure 6.
Figure 5 shows a simplified diagram of the sensing circuit. The voltage across the 1
=sense resistor is
differentially amplified and converted into a single-ended voltage with respect to ground. This is fed into
a bank of comparators and measured against a reference voltage. The circuit takes a measurement each
time TCS is driven below a 0.8 volts threshold and the outputs are latched on the rising edge of TCS. If
IBUS is greater than 32 mA, the DS21T09 will be isolated from the SCSI bus. It is recommended that the
signal on TCS be asserted for at least 25
sec to allow the signal (and comparator outputs) to settle into a
known state. A timing diagram of the sensing and latching operation is shown in Figure 7.
It is preferred that the -RST line be used for monitoring the bus termination status because -RST is only
asserted during power up or during a major change in bus configuration. Note that R14 will have a higher
input capacitance than the other lines because of the additional circuitry required for bus sensing.
The DS21T09 will be isolated from the SCSI bus as shown in Table 2.
BUS CURRENT SENSING CIRCUITRY Figure 5
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS21T09S/T&R | 制造商:Maxim Integrated Products 功能描述:IC TERMINATOR SCSI P&P 28-SOIC |
| DS21T09S/T&R | 功能描述:IC TERMINATOR SCSI P&P 28-SOIC RoHS:否 類別:集成電路 (IC) >> 接口 - 信號(hào)終端器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:50 系列:- 類型:SCSI，SE 端子數(shù):9 電源電壓:4 V ~ 5.25 V 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:16-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC 包裝:管件 |
| DS21T09S+ | 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 |
| DS21T11 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Terminator |
| DS21T11S | 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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