DS2120

Manufacturer Part NumberDS2120
DescriptionUltra3 LVD SCSI Terminator
ManufacturerDallas Semiconducotr
DS2120 datasheet
 


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FEATURES
§ Fully compliant with Ultra3, Ultra160,
Ultra320, and Ultra2 (LVD only) SCSI
§ Provides low-voltage differential (LVD)
termination for nine signal line pairs
§ Zero-temperature coefficient-termination
resistors
§ Auto-select of LVD termination
§ 5% tolerance on LVD termination resistance
§ Low power-down capacitance of 3pF
§ Built- in mode change filter/delay
§ On-board thermal-shutdown circuitry
§ SCSI bus hot-plug compatible
APPLICATIONS
§ Raid Systems
§ SCSI Host Bus Adapter Cards (HBA)
§ Servers
§ SCSI Cables
§ Network Attached Storage (NAS)
§ Storage Area Networks (SANs)
ORDERING INFORMATION
DS2120E
28-Pin TSSOP
DS2120B
36-Pin SSOP
DESCRIPTION
The DS2120 Ultra3 LVD SCSI terminator is a low-voltage differential (LVD) terminator. If the device is
connected in an LVD-only bus, the DS2120 uses LVD termination. If any single-ended (SE) or high-
voltage differential (HVD) devices are connected to the bus, the DS2120 disconnects from the bus. This
is accomplished inside the part automatically by sensing the voltage on the SCSI bus DIFFSENS line.
For the LVD termination, the DS2120 integrates two current sources with nine precision resistor strings.
Three DS2120 terminators are needed for a wide SCSI bus.
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple
revisions of any device may be simultaneously available through various sales channels. For information about device
errata, click here: http://dbserv.maxim-ic.com/errata.cfm.
Ultra3 LVD SCSI Terminator
PIN ASSIGNMENT
HS GND
HS GND
HS GND
HS GND
0°C to +70°C
0°C to +70°C
1 of 10
1
28
VREF
TPWR
2
27
TPWR
R1P
26
R1N
3
R9N
25
R2P
4
R9P
24
R2N
5
R8N
23
6
R8P
R3P
HS GND
7
22
R7N
R3N
8
21
R4P
R7P
9
20
R6N
R4N
19
10
R5P
18
R6P
11
DIFF_CAP
R5N
12
17
ISO
DIFFSENSE
13
16
GND
MSTR/SLV
14
15
DS2120E 28-Pin TSSOP
1
VREF
36
TPWR
NC
2
35
NC
LVD
3
34
NC
NC
4
33
R1P
R9N
R1N
5
32
R9P
R2P
6
31
R2N
R8N
7
30
R8P
8
29
HS GND
9
28
HS GND
10
27
R3P
HS GND
11
26
R7N
R3N
12
25
R4P
13
R7P
24
R4N
R6N
14
23
R5P
R6P
15
22
R5N
DIFF_CAP
16
21
ISO
DIFFSENSE
17
20
GND
MSTR/SLV
18
19
DS2120B 36-Pin SSOP
DS2120
042602

DS2120 Summary of contents

  • Page 1

    ... The DS2120 Ultra3 LVD SCSI terminator is a low-voltage differential (LVD) terminator. If the device is connected in an LVD-only bus, the DS2120 uses LVD termination. If any single-ended (SE) or high- voltage differential (HVD) devices are connected to the bus, the DS2120 disconnects from the bus. This is accomplished inside the part automatically by sensing the voltage on the SCSI bus DIFFSENS line ...

  • Page 2

    ... TERMPWR and V and a 0.01 F high- frequency capacitor are recommended between TPWR and ground and placed as close as possible to the DS2120. The DS2120 should be placed as close as possible to the SCSI connector to minimize signal and power trace length, thereby lessening input capacitance and reflections that can degrade the bus signals ...

  • Page 3

    ... DIFFSENS control line, thereby eliminating erroneous switching between modes. This filter eliminates the need for the external capacitor and resistor, which previously performed this function. The external filter can be used in addition to the digital filter if the DS2120 and DS2118M or DS2119M are to be used interchangeably. ...

  • Page 4

    ... Figure 1. BLOCK DIAGRAM 2.15V DIFF CAP 0.6V THERMAL SHUTDOWN ISO MSTR/SLV Mode Change Delay/Filter 1.30V CONTROL LOGIC I_GEN 2.15V REFERENCE 1.30V GENERATOR 0.6V 1.25V VREF DS2120 LVD DIFFSENSE R1N R1P R9N R9P ...

  • Page 5

    ... Figure 2. SCSI BUS CONFIGURATION DS2120 ...

  • Page 6

    ... Table 1. PIN DESCRIPTION DS2120E 28-Pin TSSOP PIN NAME 1 VREF 2–5, 7–12, RxP, RxN 18–21, 23– HS_GND 13 ISO 14 GND 15 MSTR/SLV 16 DIFFSENSE 17 DIFF_CAP 27, 28 TPWR DS2120B 36-Pin SSOP PIN NAME 1 VREF 4–7, 11–16, RxP, RxN 22–25, 29–32 8–10, 26–28 ...

  • Page 7

    ... MAX UNITS 110 ? 190 ? 125 mV 1.375 MAX UNITS µA 1.0 µA -1 1 200 µA +125 µA +6.5 µA 150 °C DS2120 NOTES 13 13 NOTES NOTES 2, 3 14 10, 11 ...

  • Page 8

    ... RC time constant formed by the resistor connected from DIFFSENSE to CD DIFF_CAP and the capacitor connected from DIFF_CAP to ground. 13) MSTR/SLV and ISO pins. 14) Terminator pins only. 15) DIFFCAP pin only. SYMBOL MIN TYP LI 1.0 REG LO 1.3 REG I LIM I SINK DS2120 MAX UNITS NOTES 2.0 % 3.5 % 200 mA 200 mA ...

  • Page 9

    ... DS2120E 28-PIN TSSOP PACKAGE DIM MIN MAX A - 1. 0.75 1.05 c 0.09 0.20 L 0.50 0.75 e1 0.65 BSC b 0.18 0.30 D 9.60 9.80 E1 4.40 BSC E 6.20 6.60 Dimensions are in millimeters (mm). NOTES: 1) Dimension D does not include mold mismatch, flash, or protrusions. Mold mismatch, flash, and protrusions shall not exceed 0.15 per side. 2) Dimension B does not include dambar protrusion. Dambar protrusion shall not be located on the lower radius of the foot ...

  • Page 10

    ... DS2120B 36-PIN SSOP PACKAGE DIM MIN MAX A 2.44 2. 0.29 0.43 c 0.23 0.32 D 15.20 15.54 E 10.11 10.52 E1 7.40 7.60 e 0.80 BSC h 0.25 0.71 L 0.51 1.02 Dimensions are in millimeters (mm). NOTES: 1) Dimensions D and E1 include mold mismatch, but do not include mold flash, protrusions, or gate burrs. Mold flash, protrusions or gate burrs shall not exceed 0.254mm per side. ...