DS2125-C01/T&R ,Ultra3 LVD/SE 15-Line SCSI TerminatorAPPLICATIONS HS_GND HS_GNDHS_GND HS_GNDHS_GND HS_GNDRaid Systems VREF TPWRR1P R15NSCSI Host Bus Ad ..
DS21348G ,3.3V E1/T1/J1 line interfaceTABLE OF CONTENTS1. LIST OF FIGURES. 42. LIST OF TABLES .. 53. INTRODUCTION... 63.1 DOCUMENT REVISI ..
DS21348G+ ,3.3V E1/T1/J1 Line Interfaceapplications. Throughout the data sheet, J1 is represented wherever T1 exists. Receive sensitivity ..
DS21348GN ,3.3V E1/T1/J1 line interfaceapplications.Throughout the data sheet, J1 is represented wherever T1 exists. Receive sensitivity a ..
DS21348GN+ ,3.3V E1/T1/J1 Line Interfaceapplications. The crystal-less on-board jitter attenuator requires only a 2.048MHz MCLK for both E1 ..
DS21348T , 3.3V E1/T1/J1 Line Interface
DS2125-C01/T&R
Ultra3 LVD/SE 15-Line SCSI Terminator
GENERAL DESCRIPTION The DS2125 Ultra3 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 DS2125 uses
LVD termination. If any SE devices are connected to
the bus, the DS2125 uses SE termination, which is
accomplished automatically inside the part by
sensing the voltage on the SCSI bus DIFFSENS line.
For the LVD termination, the DS2125 integrates two
current sources with 15 precision resistor strings. For
the SE termination, one regulator and 15 precision
110Ω resistors are used. Two DS2125 terminators
are needed for a wide SCSI bus.
APPLICATIONS Raid Systems
SCSI Host Bus Adapter (HBA) Cards
Servers
SCSI Cables
Network Attached Storage (NAS)
Storage Area Networks (SANs)
FEATURES �
Fully Compliant with Ultra3 SCSI �
Provides Multimode Low-Voltage
Differential/Single-Ended (LVD/SE)
Termination for 15 Signal Line Pairs �
Auto-Selection of LVD or SE Termination �
5% Tolerance on SE and LVD Termination
Resistance �
Low 3pF Power-Down Capacitance �
On-Board Thermal-Shutdown Circuitry �
SCSI Bus Hot-Plug Compatible �
Fully Supports Actively Negated SE SCSI
Signals
PIN CONFIGURATION
ORDERING INFORMATION
PART* PIN-PACKAGE TOP MARK** DS2125 48 LQFP DS2125
DS2125+ 48 LQFP DS2125
DS2125/T&R 48 LQFP/Tape and Reel DS2125
DS2125+T&R 48 LQFP/Tape and Reel DS2125
*All devices rated over the commercial operating temperature
range, 0°C to +70°C.
**The top mark includes a “+” for lead-free packages.
+Denotes lead-free/RoHS-compliant package.
DS2125
Ultra3 LVD/SE SCSI 15-Line Terminator
R14N
R14P
R13N
R13P
R12N
R12P
R11N
R11P
R10N
R10P
R9N
R9P2627282930 31 32 33 34 35362 3 4 5 6 7 89101112
R15P
HS_GND
HS_GND
HS_GND
R15N
TPWR
HS_GND
HS_GND
HS_GND
VREF
R1P
R1N
R2P
R2N
R3P
R3N
R4P
R4N
R5P
R5N
R6P
R6N
R7P
R7N
HS_GND
HS_GND
HS_GND
ISO
DIFFSENSE
HS_GND
HS_GND
HS_GND
R8P
R8N
GNDDIFF_CAP
Dallas
Semiconductor DS2125
LQFP (1.4mm) TOP VIEW
DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator
ABSOLUTE MAXIMUM RATINGS VREF, ISO, GND, DIFFSENSE, DIFF_CAP, TPWR, RxP, RxN (x = 1 . . . 15)………………………………-0.3V, +6.0V
VREF Continuous Output Current………………………………………………………………………………………±200mA
Continuous Power Dissipation (TA = +70°C), 48-Pin LQFP……………………………………………………………...2W
Operating Temperature Range………………………………………………………………………………….0°C to +70°C
Junction Temperature…………………………………………………………………………………………………...+150°C
Storage Temperature Range………………………………………………………………………………...-65°C to +160°C
Lead Temperature (soldering, 10s)…………………………………………………………………………………….+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS (TPWR = 3.3V, TA = 0°C to +70°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS LVD 2.7 5.5 TPWR Operating Supply
Range VTPWR SE 4.0 5.5 V
TPWR SUPPLY CURRENT ITPWR_LVD LVD SCSI mode 20 32 mA
ITPWR_SE SE SCSI mode 1.6 10 mA TPWR Supply Current
(All Lines Open) ITPWR_ISO ISO mode (terminators disabled) 250 750 µA
LVD TERMINATION (Applies to each line pair, 1 to 15 in LVD mode) Differential-Mode
Termination Resistance RDM 100 110 Ω
Common-Mode
Termination Resistance RCM RP and RN shorted together 110 165 Ω
Differential-Mode Bias VDM All lines open 100 125 mV
Common-Mode Bias VCM RP and RN shorted together 1.15 1.25 1.35 V
SE TERMINATION (Applies to SE terminators, 1 to 15 in SE mode) Single-Ended Mode
Termination Resistance RSE
RSE = (VLx - 0.2) / ILx,
where VLx = voltage at terminator
pin with pin unloaded and
ILx = current for each terminator pin
with the pin forced to 0.2V (Note 2)
104.5 110 115.5 Ω
Signal level at 0.2V, all lines low -21.0 -24 -25.4 Termination Current
(Note 2) ISE Signal level at 0.5V -18.0 -22.4 mA
SE Voltage Reference VREF (Note 2) 2.7 2.85 3.0 V
Pin Leakage With ISO high 400 nA
Single-Ended GND
Resistance RGND Measured at RP pins, I = 10mA 20 60 Ω
TERMINATOR PIN CAPACITANCE Terminator Pin
Capacitance CIN With ISO high (Note 1) 3 pF
VREF REGULATOR 1.25V Regulator Output
Voltage VREF_LVD 1.15 1.25 1.35 V
1.25V Regulator Short-
Circuit Source Current ISOURCE VREF = 0V -375 -700 -1000 mA
1.25V Regulator Short-
Circuit Sink Current ISINK VREF = 3.3V 170 300 700 mA
1.25V Regulator Line
Regulation VREF unloaded; vary TPWR from
2.7V to 5.5V 1.0 2.5 %
2.85V Regulator (Note 2) 2.7 2.85 3.0 V
2.85V Regulator Short-
Circuit Source Current VREF = 0V (Note 2) -375 -700 -1000 mA
DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator
ELECTRICAL CHARACTERISTICS (continued) (TPWR = 3.3V, TA = 0°C to +70°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VREF REGULATOR 2.85V Regulator Line
Regulation
VREF unloaded; vary TPWR from
4.0V to 5.5V 1.0 2.5 %
DIFFSENS OUTPUT DIFFSENS Driver Output
Voltage VDSO -5mA ≤ IDFFSENS ≤ 50µA 1.2 1.4 V
DIFFSENS Driver Source
Current IDSH VDIFFSENS = 0V -15 -5 mA
DIFFSENS Driver Sink
Current IDSL VDIFFSENS = 3.3V 100 200 µA
ILEAK, LOW With ISO high, |VDIFFSENS| = 0.3V -3 +1 DIFFSENS Leakage
(Note 3) ILEAK, HIGH With ISO high, |VDIFFSENS - VTPWR| =
0.3V 1 3 µA
THERMAL SHUTDOWN Thermal-Shutdown
Threshold For increasing temperature
(Note 1) 150 °C
Thermal-Shutdown
Hysteresis (Note 1) 10 °C
MODE CHANGE DELAY/FILTER Mode Change Delay tDELAY 0.66 1.25 2.00 ms
LOGICAL SIGNALS (ISO) Input Low Voltage VIL -0.3 +0.8 V
Input High Voltage VIH 2 TPWR
+ 0.3 V
Input Current IIL VCC = 3.3V -30 -10 µA
DIFF_CAP Input Current IL VIL = -0.3V -1 +1 µA
DIFF_CAP SE
Operating Range VSEOR -0.3 +0.5 V
DIFF_CAP LVD
Operating Range VLVDOR 0.7 1.9 V
DIFF_CAP HVD
Operating Range VHVDOR 2.4 VTPWR +
0.3 V
Note 1: Guaranteed by design.
Note 2: TPWR = 4.0V.
Note 3: Room temperature only.
PIN DESCRIPTION
PIN NAME FUNCTION 1, 2, 11–26,
37–48 RxP, RxN Signal Termination. Connect to SCSI bus signal lines.
3 TPWR Termination Power. Connect to the SCSI TERMPWR line and decouple with a 2.2µF
capacitor.
4–9, 28–33 HS_GND Heat-Sink Ground. Internally connected to the mounting pad. This should be grounded.
10 VREF Reference Voltage. 2.85V reference in SE mode and 1.25V reference in LVD mode; must be
decoupled with a 4.7µF capacitor.
27 GND Ground. Signal ground, 0V.
34 DIFF_CAP DIFFSENSE Capacitor. Connect a 0.1µF capacitor for the DIFFSENSE filter. Input to detect
the type of device (differential or single-ended) on the SCSI bus.
35 DIFFSENSE DIFFSENSE. Output to drive the SCSI bus DIFFSENS line.
DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator
Figure 1. Block Diagram R1N
R15P
R15N
R1P
Dallas
Semiconductor DS2125
ISODIFFSENSE
DIFF_CAP
VREF
THERMAL-
SHUTDOWN
CIRCUITRY
CONTROL
LOGIC
DIFFENSE
CIRCUITRY
BANDGAP
1.25V
10Ω
10Ω
VREF
SE
LVD
HVD
SE GND
DRIVER
DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator
Figure 2. SCSI Bus Configuration
Note: The following terms are used throughout this data sheet: DIFFSENS: Refers to the SCSI bus signal.
DIFFSENSE: Refers to the DS2125 pin name and internal circuitry capable of driving the DIFFSENS line.
DIFF_CAP: Refers to the DS2125 pin name and internal circuitry relating to monitoring the DIFFSENS line.
DETAILED DESCRIPTION The DS2125 combines LVD and SE termination with DIFFSENSE sourcing and detection. A bandgap reference is
fed into two amplifiers, which creates a 1.25V reference voltage and a 2.85V reference voltage. The control logic
determines which of these references are applied to the termination resistors. If the SCSI bus is in LVD mode, the
1.25V reference is used. If the SCSI bus is in SE mode, the 2.85V reference is used. That same control logic
switches in/out parallel resistors to change the total termination resistance accordingly. Finally, in SE mode the Rp
pins are switched to ground.
The DIFFSENSE circuitry decodes trinary logic. There is one of three voltages on the SCSI control line called
DIFFSENS. Two comparators and a NAND gate determine if the voltage is below 0.6V, above 2.15V, or in
between, which indicates the mode of the bus as SE, HVD, or LVD, respectively.
TERMPWR TERMPWR
4.7µF 0.1µF
DIFFSENSE
TPWR
ISO
VREF DIFF_CAP
DIFFSENS
4.7µF
TPWR
ISO
VREF DIFF_CAP
DIFFSENS
CONTROL LINES (15)
0.1µF
TPWR
ISO
VREF DIFF_CAP
DIFFSENS
4.7µF 4.7µF
TPWR
ISO
VREF DIFF_CAP
DIFFSENS
CONTROL LINES (15)
20kΩ 20kΩ
DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator
The DS2125’s DIFF_CAP pin monitors the DIFFSENS line to determine the device’s proper operating mode. The
DIFFSENSE pin can also drive the SCSI DIFFSENS line to determine the SCSI bus-operating mode. The DS2125
switches to the termination mode that is appropriate for the bus based on the value of the DIFFSENS voltage.
These modes are LVD mode, SE mode, and HVD isolation mode.
LVD MODE A precision laser-trimmed resistor string with two amplifiers provides LVD termination. This configuration yields
105Ω differential and 150Ω common-mode impedance. A 112mV fail-safe bias is maintained when no drivers are
connected to the SCSI bus.
SE MODE When the external driver for a given signal line turns off, the active terminator pulls that signal line to 2.85V
(quiescent state). The terminating resistors maintain their 110Ω value.
HVD ISOLATION MODE The DS2125 identifies that there is an HVD device on the SCSI bus and isolates the termination pins from the bus.
When ISO is pulled high, the termination pins are isolated from the SCSI bus, and VREF remains active. During
thermal shutdown, the termination pins are isolated from the SCSI bus, and VREF becomes high impedance. The
DIFFSENSE driver is shut down during either of these two events. An internal pulldown resistor assures that the
DS2125 is terminating the bus if the ISO pin is left floating.
To ensure proper operation, the TPWR pin should be connected to the SCSI bus TERMPWR line. As with all
analog circuitry, the TERMPWR and VDD lines should be bypassed locally. A 2.2µF capacitor and a 0.01µF high-
frequency capacitor are recommended between TPWR and ground, and placed as close as possible to the
DS2125. The DS2125 should be placed as close as possible to the SCSI connector to minimize signal and power
trace length, thereby resulting in less input capacitance and reflections, which can degrade the bus signals.
To maintain the specified regulation, a 4.7µF capacitor is required between the VREF pin and ground of each
DS2125. A high-frequency capacitor (0.1µF ceramic recommended) can also be placed on the VREF pin in
applications that use fast rise/fall-time drivers. Figure 2 shows a typical SCSI bus configuration.
REFERENCE DOCUMENTS
TITLE T10 PROJECT
DOCUMENT T10 COMMITTEE FTP LINK ANSI
DOCUMENT NO. SCSI Parallel Interface 2 (SPI-2) Project: 1142-M, 1998 ftp://ftp.t10.org/t10/drafts/spi2/spi2r20b.pdf X3.302:1998
SCSI Parallel Interface 3 (SPI-3) Project: 1302-D, 1999 ftp://ftp.t10.org/t10/drafts/spi3/spi3r14.pdf NCITS.336:2000
SCSI Parallel Interface 4 (SPI-4) Project: 1365-D, 200x ftp://ftp.t10.org/t10/drafts/spi4/spi4r10.pdf INCITS.362:2002
SUPPLIERS
SUPPLIER PHONE WEBSITE American National Standards Institute (ANSI) 212-642-4900 www.ansi.org/
Global Engineering Documents 800-854-7179 http://global.ihs.com/
CHIP INFORMATION TRANSISTOR COUNT: 8382 MOS and 87 BiPOLAR
PROCESS: BiCMOS
SUBSTRATE CONNECTED TO GROUND
THERMAL INFORMATION Theta-JA: 65°C/W
