General Description
The IMP2119 is a multimode SCSI terminator that conforms to the SCSI Parallel Interconnect-2 (SPI-2) specification developed by the T10 standards committee for low voltage differential (LVD) termination. Multimode compatibility permits the use of legacy devices on the bus without hardware alterations. Automatic mode selection is achieved through voltage detection on the diffsense line.
The IMP2119 delivers the ultimate in SCSI bus performance while saving component cost and board area. Elimination of the external capacitors also mitigates the need for a lengthy capacitor selection process. The individual high bandwidth drivers also maximize channel separation and reduce channel to channel noise and cross talk. The high bandwidth architecture insures ULTRA3 performance.
When the IMP2119 is enabled, the differential sense (DIFFSENSE) pin supplies a voltage between 1.2V and 1.4V. In application, this pin is tied to the DIFFSENSE input of the corresponding LVD transceivers. This action enables the LVD transceiver function. DIFFSENSE is capable of supplying a maximum of 15mA. Tying the DIFFSENSE pin HIGH places the IMP2119 in a high impedance state indicating the presence of an HVD device. Tying the pin LOW places the part in a single-ended mode while also signaling the multimode transceiver to operate in a singleended mode.
Recognizing the needs of portable and configurable peripherals, the IMP2119 have a TTL compatible sleep/disable mode. During this sleep/disable mode, power dissipation is reduced to a meager 15μA while also placing all outputs in a high impedance state. Also during sleep/disable mode, the DIFFSENSE function is disabled and is placed in a high impedance state.
Another key feature of the IMP2119 is the master/slave function. Driving this pin HIGH or floating the pin enables the 1.3V DIFFSENSE reference. Driving the pin LOW disables the on board DIFFSENSE reference and enables use of an external master reference device.

Key Features
*Auto-selectable LVD or single-ended termination
*3.0pF maximum disabled output capacitance
*Fast response, no external capacitors required
*Compatible with active negation drivers
*15μA supply current in disconnect mode
*Logic command disconnects all termination lines
*DIFFSENSE line driver
*Ground driver integrated for single-ended operation
*Current limit and thermal protection
*Hot-swap compatible (single-ended)
*Compatible with SCSI, SPI-2, SPI-3, SPI-4 ULTRA160 and ULTRA320
*Pin compatible with DS2119

IMP2119CPW

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DESCRIPTION
 The 9-channel IMP5218 SCSI terminator is part of IMP's family of highperformance SCSI terminators that deliver true UltraSCSI performance.
The BiCMOS design offers superior performance over first generation linear regulator/resistor based terminators.
The IMP5218 has two disconnect pins for SCSI Plug and Play (PnP) applications.
IMP's new architecture employs high-speed adaptive elements for each channel, thereby providing the fastest response possible - typically 35MHz, which is 100 times faster than the older linear regulator terminator approach.
The bandwidth of terminators based on the older regulator/resistor terminator architecture is limited to 500kHz since a large output stabilization capacitor is required.
The IMP architecture eliminates the external output compensation capacitor and the need for transient output capacitors while maintaining pin compatibility with first generation designs. Reduced component count is inherent with the IMP5218.
The IMP5218 architecture tolerates marginal system designs.
A key improvement offered by the IMP5218 lies in its ability to insure reliable, error-free communications even in systems which do not adhere to recommended SCSI hardware design guidelines, such as improper cable lengths and impedance.
Frequently, this situation is not controlled by the peripheral or host designer.
For portable and configurable peripherals, the IMP5218 can be placed in a sleep mode with two disconnect signals.
When disabled, the quiescent current is typically 375μA, and the outputs are in a high impedance state.

Key Features
* SCSI plug and play
- Dual disconnect pins
- Logic LOW disconnects lines
* Hot swap compatible
* Ultra-Fast response for Fast-20 SCSI applications
* 35MHz channel bandwidth
* 3.5V operation
* Less than 3pF output capacitance
* 375μA disable-mode current
* Thermally self limiting
* No external compensation capacitors
* Implements 8-bit or 16-bit (wide) applications
* Compatible with active negation drivers (60mA/channel)
* Compatible with passive and active terminations
* Approved for use with SCSI 1, 2, 3 and UltraSCSI

IMP5218CDW
IMP5218CDWT
IMP5218CPW
IMP5218CPWT

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PRODUCT DESCRIPTION
 The ALPHA Semiconductor AS1117 is a low power positive-voltage regulator designed to meet 800mA output current and comply with SCSI-II specifications with a fixed output voltage of 2.85V. This device is an excellent choice for use in battery-powered applications, as active terminators for the SCSI bus, and portable computers.
The AS1117 features very low quiescent current and very low dropout voltage of 1.2V at a full load and lower as output current decreases.
AS1117 is available as an adjustable or fixed 2.85V, 3V, 3.3V, and 5V output voltages.
The AS1117 is offered in a 3-pin surface mount package SOT-223, TO-252, TO-220, SOT-89 & TO-263.
The output capacitor of 10mF or larger is needed for output stability of AS1117 as required by most of the other regulator circuits.
Use of ALPHA Semiconductor’s design, processing and testing techniques make our AS1117 superior over similar products.

FEATURES
* Guaranteed 800mA Output
* Three Terminal Adjustable Or Fixed 1.5V, 2.5V, 2.85V, 3V, 3.3V & 5V
* Very Low Quiescent Current
* Low Dropout Voltage Of 1.2 Volts At Full Load
* Extremely Tight Load And Line Regulation
* Very Low Temperature Coefficient
* Fixed 2.85V Device For SCSI-II Active Terminator
* Logic-Controlled Electronic Shutdown
* Internal Overcurrent Limiting & Thermal Overload Protection
* Surface Mount Package SOT-223, TO-252, TO-220, SOT-89, TO-263, & SO-8

APPLICATIONS
* SCSI-II Active Terminator
* Portable/ Palm Top / Notebook Computers
* Battery Chargers
* Disk Drives
* Portable Consumer Equipment
* Portable Instrumentation
* SMPS Post-Regulator

AS1117U
AS1117U-X

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The 9-channel IMP5219 SCSI terminator is part of IMP's family of highperformance SCSI terminators that deliver true UltraSCSI performance.
The BiCMOS design offers superior performance over first generation linear regulator/resistor based terminators.
IMP's new architecture employs high-speed adaptive elements for each channel, thereby providing the fastest response possible - typically 35MHz, which is 100 times faster than the older linear regulator terminator approach.
The bandwidth of terminators based on the older regulator/resistor terminator architecture is limited to 500kHz since a large output stabilization capacitor is required.
The IMP architecture eliminates the external output compensation capacitor and the need for transient output capacitors while maintaining pin compatibility with first generation designs. Reduced component count is inherent with the IMP5219.
The IMP5219 architecture tolerates marginal system designs.
A key improvement offered by the IMP5219 lies in its ability to insure reliable, error-free communications even in systems which do not adhere to recommended SCSI hardware design guidelines, such as improper cable lengths and impedance.
Frequently, this situation is not controlled by the peripheral or host designer.
For portable and configurable peripherals, the IMP5219 can be placed in a sleep mode with an active LOW disable signal.
Quiescent current is typically 375μA and output are in a high impedance state when disabled.

Key Features
* Ultra-Fast response for Fast-20 SCSI applications
* Hot swap compatible
* 35MHz channel bandwidth
* 3.5V operation
* Less than 3pF output capacitance
* Sleep-mode current less than 375μA
* Thermally self limiting
* No external compensation capacitors
* Implements 8-bit or 16-bit (wide) applications
* Compatible with active negation drivers (60ma/channel)
* Compatible with passive and active terminations
* Approved for use with SCSI 1, 2, 3 and UltraSCSI

IMP5219CDW
IMP5219CDWT
IMP5219CPW
IMP5219CPWT

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FEATURES
• Fully compliant with SCSI and SCSI-2 standards
• Backward compatible to the DS2107S
• Provides active termination for 9 signal lines
• Laser-trimmed 110 ohm termination resistors have 1% tolerance
• Low dropout voltage
• Power-down mode isolates termination resistors from the bus
• Handles actively negated SCSI signals
• Onboard thermal shutdown circuitry
• 16-pin plastic SOIC (DS2107AS) and 20-pin plastic thin SSOP (DS2107AE)

DESCRIPTION
The SCSI-2 standard recommends the use of active terminations at both ends of every cable segment in a SCSI system with single-ended drivers and receivers.
The DS2107A SCSI Terminator, which is fully compliant with the standard, enables the designer to gain the benefits of active termination: greater immunity to voltage drops on the TERMPWR (TERMination PoWeR) line, enhanced high-level noise immunity, intrinsic TERMPWR decoupling, and very low quiescent current consumption. The DS2107A integrates a regulator and nine precise switched 110 ohm termination resistors into a monolithic IC.

FUNCTIONAL DESCRIPTION
The DS2107A consists of a bandgap reference, buffer amplifier, and nine termination resistors (Figure 1). The bandgap reference circuit produces a precise 2.55V level which is fed to a buffer amplifier. The buffer produces a 2.85V level and is capable of sourcing at least 24 mA into each of the termination resistors when the signal line is low (active). When the driver for a given signal line turns off, the terminator will pull the signal line to 2.85V (quiescent state). To handle actively negated SCSI signals, the buffer can sink 200 mA. When all lines settle in the quiescent state, the regulator will consume about 5 mA. When the DS2107A is put into powerdown mode by bringing PD low, the power-down circuitry will turn off the transistors on each signal line. This will isolate the DS2107A from the signal lines and effectively remove it from the circuit. The power-down pin (PD) has an internal 50K ohm pull-up resistor. To place the DS2107A into an active state, the PD pin should be left open circuited.
To ensure proper operation, both the TERMPWR1 and TERMPWR2 pins must be connected to the SCSI bus TERMPWR line and both the VREF1 and VREF2 pins must be tied together externally. Each DS2107A requires parallel 0.1 mF and 4. 7 mF capacitors connected between the VREF pins and ground. Figure 2 details a typical SCSI bus configuration. In an 8-bit wide SCSI bus arrangement (“A” Cable), two DS2107A’s would be needed at each end of the SCSI cable in order to terminate the 18 active signal lines. In a 16-bit wide SCSI bus arrangement (“P” Cable), three DS2107A’s would be needed at each end of the SCSI cable in order to terminate the 27 active signal lines.


DS2107AS
DS2107AE

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