DS21T11
PRODUCTION
DS21T11
SCSI Terminator
FEATURES
PIN ASSIGNMENT
• Fully
compliant with SCSI–1, Fast SCSI and
Ultra SCSI
• Provides active termination for 18 signal lines
• Low power down capacitance of 3 pF
• Onboard thermal shutdown circuitry
• SCSI bus hot plug compatible
• Fully supports actively negated SCSI signals
GND
27
R18
R2
3
26
R17
R3
4
25
R16
R4
5
24
R15
R5
6
23
R14
HS–GND
7
22
HS–GND
HS–GND
8
21
HS–GND
HS–GND
9
20
HS–GND
R6
10
19
R13
R7
11
18
R12
12
17
R11
13
16
R10
TPWR
• 5% tolerance on termination current
28
2
R9
tolerance on termination resistors and voltage
regulator
1
R1
R8
• 5%
PD
14
15
VREF
DS21T11S 28–PIN SOIC (300 MIL)
DESCRIPTION
Fast SCSI and Ultra SCSI require the use of active terminations at both ends of every cable segment in a
SCSI system with single–ended drivers and receivers.
Ultra SCSI requires support of active negation and hot
plugging. The DS21T11 is fully compliant with these
standards.
Active termination provides: 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. One DS21T11 can be used to terminate
the Narrow SCSI bus, and a DS21T07 can be used with
a DS21T11 for termination of a Wide SCSI bus.
The DS21T11 integrates a low drop–out regulator and
18 precise switched 110 ohms termination resistors into
a 28–pin 300 mil SOIC package.
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