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DS2120E Schematic ( PDF Datasheet ) - Dallas Semiconducotr

Teilenummer DS2120E
Beschreibung Ultra3 LVD SCSI Terminator
Hersteller Dallas Semiconducotr
Logo Dallas Semiconducotr Logo 




Gesamt 10 Seiten
DS2120E Datasheet, Funktion
www.maxim-ic.com
DS2120
Ultra3 LVD SCSI Terminator
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
PIN ASSIGNMENT
VREF
R1P
R1N
R2P
R2N
HS GND
R3P
R3N
R4P
R4N
R5P
R5N
ISO
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28 TPWR
27 TPWR
26 R9N
25 R9P
24 R8N
23 R8P
22 HS GND
21 R7N
20 R7P
19 R6N
18 R6P
17 DIFF_CAP
16 DIFFSENSE
15 MSTR/SLV
DS2120E 28-Pin TSSOP
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 0°C to +70°C
DS2120B 36-Pin SSOP 0°C to +70°C
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 TPWR
35 NC
34 LVD
33 NC
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
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.
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DS2120E Datasheet, Funktion
Table 1. PIN DESCRIPTION
DS2120
DS2120E 28-Pin TSSOP
PIN NAME
1
2–5, 7–12,
18–21, 23–26
6, 22
VREF
RxP, RxN
HS_GND
13 ISO
14 GND
15 MSTR/SLV
16 DIFFSENSE
17 DIFF_CAP
27, 28
TPWR
DESCRIPTION
Regulator Output Voltage. 1.25V reference in LVD mode; must be
decoupled with a 4.7µF cap.
Signal Termination. Connect to SCSI bus signal lines.
Heat Sink Ground. Internally connected to the mounting pad. Should be
connected to ground.
Isolation. When pulled high, terminating resistors and biasing current sources
are isolated from the SCSI bus.
Signal Ground.
Master/Slave. Mode select for the noncontrolling terminator. When pulled
high (MSTR), the DIFFSENS driver is enabled.
DIFFSENSE. Output to drive the SCSI bus DIFFSENS line.
DIFFSENSE Capacitor. Connect a 0.1µF capacitor for DIFFSENSE filter.
Input to detect the type of device (differential or single -ended) on the SCSI
bus.
Termination Power. Connect to the SCSI TERMPWR line and decouple with
2.2µF capacitor.
DS2120B 36-Pin SSOP
PIN NAME
1 VREF
2, 3, 33, 35
4–7, 11–16,
22–25, 29–32
8–10, 26–28
NC
RxP, RxN
HS_GND
17 ISO
18 GND
19 MSTR/SLV
20 DIFFSENSE
21 DIFF_CAP
34 LVD
36 TPWR
DESCRIPTION
Regulator Output Voltage. 1.25V reference in LVD mode; must be
decoupled with a 4.7µF cap.
No Connect. Do not connect pins.
Signal Termination. Connect to SCSI bus signal lines.
Heat Sink Ground. Internally connected to the mounting pad. Should be
connected to ground.
Isolation. When pulled high, terminating resistors and biasing current sources
are isolated from the SCSI bus.
Signal Ground.
Master/Slave. Mode select for the noncontrolling terminator. When pulled
high (MSTR), the DIFFSENS driver is enabled.
DIFFSENSE. Output to drive the SCSI bus DIFFSENS line.
DIFFSENSE Capacitor. Connect a 0.1µF capacitor for DIFFSENSE filter.
Input to detect the type of device (differential or single ended) on the SCSI
bus.
Low-Voltage Differential. Output of DIFFSENSE receiver; output high
indicates LVD bus operation .
Termination Power. Connect to the SCSI TERMPWR line and decouple with
2.2µF capacitor.
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