DS21T07
SCSI Terminator
www.dalsemi.com
FEATURES
Fully compliant with SCSI–1, Fast SCSI and
Ultra SCSI
Backward compatible to the DS2107,
DS2107A, and DS21S07
Provides active termination for nine signal
lines
Laser–trimmed 110 ohms termination
resistors have 2% tolerance
Low dropout voltage regulator
Power–down mode isolates termination
resistors from the bus
SCSI bus hot–plug compatible
Fully supports actively negated SCSI signals
Onboard thermal shutdown circuitry
16–pin plastic SOIC (DS21T07S) and 20–pin
plastic TSSOP (Thin Shrink Small Outline
Package) (DS21T07E)
PIN ASSIGNMENT
TERMPWR1
R1
R2
R3
R4
R5
VREF1
GND
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
PD
VREF2
NC
R9
R8
R7
R6
TERMPWR2
DS21T07S 16-pin SOIC (300-mil)
TERMPWR1
HS-GND
R1
R2
R3
R4
R5
HS-GND
VREF1
GND
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
PD
VREF2
HS-GND
NC
R9
R8
R7
R6
HS-GND
TERMPWR2
DS21T07E 20-pin TSSOP (173-mil)
ACTUAL FOOTPRINT SIZE
0.41”
0.41”
0.26”
0.27”
DS21T07S
DS21T07E
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. The DS21T07 SCSI Terminator, which is fully
compliant with these standards, 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 DS21T07
integrates a regulator and nine precise switched 110 ohms termination resistors into a monolithic IC. The
DS21T07 can be electrically isolated from the SCSI bus without physical removal from the SCSI device.
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