DS2118M
Ultra2 LVD/SE SCSI Terminator
www.dalsemi.com
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
NC
NC
R1P
R1N
R2P
R2N
HS GND
HS GND
HS GND
R3P
R3N
R4P
R4N
R5P
R5N
ISO
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
TPWR
HVD
LVD
SE
R9N
R9P
R8N
R8P
HS GND
HS GND
HS GND
R7N
R7P
R6N
R6P
DIFF_CAP
DIFFSENSE
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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090199
DALLAS [ DALLAS SEMICONDUCTOR ]
