The wireless communication solution provider
Ultra Multimode LVD/SE
SCSI Terminator
FEATURES
AR7519
„Y
Meets SCSI-1, SCSI-2, Ultra2, and Ultra3/Ultra160 standards.
„Y
Auto-selectable multimode for single-ended or low voltage
differential termination.
„Y
Current limit and thermal shutdown protection.
Ground driver integrated for single-ended operation
„Y
SCSI bus hot-swap compatible.
„Y
Compatible with active negation drivers.
APPLICATIONS
PC server
Workstation
DESCRIPTION
The AR7519 multimode SCSI terminator is both a single-ended (SE) and a
low voltage differential (LVD) terminator that meets the specification of SCSI
parallel interface (SPI-3). In addition, the AR7519 provides backward
compatibility to the SCSI-1, SCSI-2, and SE specifications. The multimode
terminator contains all functions required to terminate and auto detect for
SCSI devices without hardware fluctuation. Auto-selection is achieved by
using voltage detection on the DIFFSENSE signal. The AR7519 senses the
DIFFSENSE line while sourcing the DIFFSENSE signal with the LVD levels.
The DIFFSENSE line being grounded indicates that one or more SE devices
are attached on the bus. The AR7519 switches to the termination mode that
is appropriate for the bus based on the value of the DIFFSENSE input voltage.
For the SE termination, the active terminator will pull RXN to 2.85V and
RXP to hard ground. The AR7519 can sink 22 mA per line as required
by SCSI specification. The SE resistor will maintain 110
5%. For
the LVD termination, the AR7519 integrates two current sources with
nine precision resistor strings. This architecture yields a 105
5%
differential and 226
10% common mode impedance. A fail-safe
bias of 110 mV is sustained when no drivers are connected to the SCSI
bus. If the AR7519 detects a HVD SCSI device on the bus, all the
signals will be set to a high impedance state.
Microchip MCU
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