DS2118M Datasheet, PDF (1/8 Pages) Dallas Semiconductor – Ultra2 LVD/SE SCSI Terminator

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DS2118M
Ultra2 LVD/SE SCSI Terminator
FEATURES
Fully compliant with Ultra2 SCSI
Provides Multimode Low Voltage
Differential/Single-Ended (LVD/SE)
termination for 9 signal line pairs
Auto-selection of LVD or SE termination
5% tolerance on SE and LVD termination
resistance
Low power down capacitance of 3 pF
Onboard thermal shutdown circuitry
SCSI bus hot plug compatible
Fully supports actively negated SE SCSI
signals
PIN ASSIGNMENT
VREF 1
NC 2
NC 3
R1P 4
R1N 5
R2P 6
R2N 7
HS GND 8
HS GND 9
HS GND 10
R3P 11
R3N 12
R4P 13
R4N 14
R5P 15
R5N 16
ISO 17
GND 18
36 TPWR
35 HVD
34 LVD
33 SE
32 R9N
31 R9P
30 R8N
29 R8P
28 HS GND
27 HS GND
26 HS GND
25 R7N
24 R7P
23 R6N
22 R6P
21 DIFF_CAP
20 DIFFSENSE
19 MSTR/SLV
DS2118MB 36-Pin SSOP
DESCRIPTION
The DS2118M Ultra2 LVD/SE SCSI Terminator is both a Low Voltage Differential (LVD) and Single-
Ended (SE) terminator. The multimode operation enables the designer to implement LVD in current
products while allowing the end-user SE backward compatibility with legacy devices. If the device is
connected in an LVD-only bus, the DS2118M will use LVD termination. If any SE devices are connected
to the bus, the DS2118M will use SE termination. This is accomplished automatically inside the part by
sensing the voltage on the SCSI bus DIFFSENS line.
For the LVD termination, the DS2118M integrates two regulated supplies with nine precision resistor
strings. For the SE termination, one regulator and nine precision 110-ohm resistors are used. Three
DS2118M terminators are needed for a Wide SCSI bus.
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