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Rev 1; 3/04
Ultra3 LVD/SE SCSI 14-Line Terminator
General Description
The DS2127 Ultra3 LVD/SE SCSI terminator provides low-voltage differential (LVD)/single-ended (SE) terminations for 14 SCSI lines. Through the voltage on the DIFF_CAP pin, the device detects the types of drivers on the bus. If the device is connected in an LVD-only bus, the DS2127 provides LVD termination. If any single-ended devices are connected to the bus, the DS2127 uses SE termination. If any high-voltage differential (HVD) devices are connected to the bus, the DS2127 isolates itself from the SCSI bus. The mode change has a built-in delay that is determined by an integrated SPI-3 mode change filter/delay. The terminating resistors can also be disconnected from the bus by asserting the ISO pin. For the LVD termination, the DS2127 provides 14 precisely trimmed resistors. Each resistor is biased with two current sources to a fail-safe state. For SE termination, the DS2127 provides 14 precision 110 resistors and one regulator for active-negation bias.
Features
Fully Compliant with Ultra2, Ultra3, Ultra160, and Ultra320 SCSI Standards Provides LVD/SE Termination for 14 Signal Pairs Auto-Selection of LVD or SE Termination 5% Tolerance on SE and LVD Termination Resistance Low 3pF Power-Down Capacitance Built-In Mode-Change Filter/Delay On-Board Thermal-Shutdown Circuitry SCSI Bus Hot-Plug Compatible Fully Supports Actively Negated SE SCSI Signals
DS2127
Ordering Information
PART DS2127 TEMP RANGE 0C to +70C PINPACKAGE 48 LQFP TOP MARK DS2127
Applications
SCSI Array Backplane SCSI Cables
Pin Configuration
TOP VIEW HS_GND HS_GND HS_GND HS_GND
9 8 7 6
12
11
10
5
4
3
2
R2P R2N R3P R3N R4P R4N R5P R5N R6P R6N R7P R7N
13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
1 48 47 46 45 44 43 42 41 40 39 38 37 36
HS_GND HS_GND TPWR R14N R14P R13N R13P R12N R12P R11N R11P R10N R10P R9N R9P R8N R8P ISO
R1N R1P VREF
DS2127
______________________________________________ Maxim Integrated Products
HS_GND HS_GND HS_GND HS_GND HS_GND HS_GND DIFF_CAP DIFFSENS
GND SE LVD
LQFP
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Ultra3 LVD/SE SCSI 14-Line Terminator DS2127
ABSOLUTE MAXIMUM RATINGS
Voltage Range on All Pins Relative to Ground ......-0.3V to +6.0V VREF Continuous Output Current....................................200mA Operating Temperature Range...............................0C to +70C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +160C Soldering Temperature .......................................See IPC/JEDEC J-STD-020A Specification
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 absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(TPWR = VTPWR(MIN) to VTPWR(MAX), TA = 0C to +70C, unless otherwise noted.)
PARAMETER TPWR Operating Supply Range (Note 1) TPWR SUPPLY CURRENT TPWR Supply Current (All Lines Open) ITPWR_LVD LVD SCSI mode ITPWR_SE ITPWR_ISO Differential-Mode Termination Resistance Common-Mode Termination Resistance Differential-Mode Bias Common-Mode Bias SE SCSI mode ISO mode (terminators disabled) 32 10 750 mA A SYMBOL VTPWR LVD SE CONDITIONS MIN 2.7 4 TYP 3.3 5.0 MAX 5.5 5.5 UNITS V
LVD TERMINATION (Applies to each line pair, 1 to 14 in LVD mode) RDM RCM VDM VCM RP and RN shorted together (VCM(MAX) = 2V, VCM(MIN) = 0.5V) All lines open RP and RN shorted together (Note 1) 100 110 100 1.15 1.25 110 165 125 1.35 mV V
SE TERMINATION (Applies to single-ended terminators, 1 to 14 in SE mode) Single-Ended Mode Termination Resistance 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 Signal level at 0.2V, all lines low Signal level at 0.5V With ISO high RGND CIN Measured at RP pins, I = 10mA With ISO high (Note 2) 0.5V VCM 2.0V, VCM applied to all RP and RN lines simultaneously VREF = 0V VREF = 3.3V 20
RSE
104.5
110
115.5
Termination Current SE Voltage Reference Pin Leakage Single-Ended GND Resistance TERMINATOR PIN CAPACITANCE Terminator Pin Capacitance VREF REGULATOR 1.25V Regulator Output Voltage 1.25V Regulator Short-Circuit Source Current 1.25V Regulator Short-Circuit Sink Current
ISE VREF
-21 -18 2.7
-24 2.85
-25.4 -22.4 3.0 400 60 3
mA V nA pF
VREF_LVD ISOURCE ISINK
1.15 -375 170
1.25 -700 300
1.35 -1000 700
V mA mA
2
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Ultra3 LVD/SE SCSI 14-Line Terminator
ELECTRICAL CHARACTERISTICS (continued)
(TPWR = VTPWR(MIN) to VTPWR(MAX), TA = 0C to +70C, unless otherwise noted.)
PARAMETER VREF REGULATOR 1.25V Regulator Line Regulation 2.85V Regulator 2.85V Regulator Short-Circuit Source Current 2.85V Regulator Short-Circuit Sink Current 2.85V Regulator Line Regulation DIFFSENS OUTPUT DIFFSENS Driver Output Voltage DIFFSENS Driver Source Current DIFFSENS Driver Sink Current VDSO IDSH IDSL ILEAK, DIFFSENS Leakage (Note 3)
LOW
DS2127
SYMBOL
CONDITIONS VREF unloaded; vary TPWR from 2.7V to 5.5V
MIN
TYP
MAX
UNITS
1.0 2.7 2.85 -700 300 1.0
2.5 3.0 -1000 700 2.5
% V mA mA %
VREF = 0V VREF = 3.3V VREF unloaded; vary TPWR from 2.7V to 5.5V -5mA IDIFFSENS 50A VDIFFSENS = 0V VDIFFSENS = 2.75V With ISO high, |VDIFFSENS| = 0.3V With ISO high, |VDIFFSENS - VTPWR| = 0.3V
-375 170
1.2 -15 100 -3 1
1.4 -5 200 +1
V mA A
A 3
ILEAK,
HIGH
THERMAL SHUTDOWN Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis MODE CHANGE DELAY/FILTER Mode Change Delay LOGICAL SIGNALS (ISO) Input Low Voltage Input High Voltage Input Current STATUS BITS (LVD, SE) Source Current Sink Current DIFF_CAP Input Current DIFF_CAP SE Operating Range DIFF_CAP LVD Operating Range DIFF_CAP HVD Operating Range IL VSEOR VLVDOR VHVDOR VIL = -0.3V -1 -0.3 0.7 2.4 +1 +0.5 1.9 VTPWR + 0.3 A V V V IOH IOL VCC = 3.3V, VLOAD = 2.4V VCC = 3.3V, VLOAD = 0.4V -4 2 -6 5 mA mA VIL VIH IIL VCC = 3.3V -0.3 2.0 -30 -10 +0.8 TPWR + 0.3 V V A tDELAY 0.66 1.25 2.00 ms For increasing temperature 130 10 C C
Note 1: All voltages are referenced to ground. Note 2: Guaranteed by design and not production tested. Note 3: Room temperature only.
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3
Ultra3 LVD/SE SCSI 14-Line Terminator DS2127
2.15V DELAY/ FILTER 0.6V LVD SE HVD SE SE LVD LVD
DIFF_CAP
LVD SE HVD THERMAL SHUTDOWN ISO 10A CONTROL LOGIC 110 52 R1N 124 REFGEN AND TRIM 1.25V (LVD) SE HVD/ISO LVD 2.85V (SE) 124 52 2.15V 1.30V 0.6V 110 52 R14N R14P 52 R1P 1.30V DIFFSENS
DS2127
BANDGAP
ALL SWITCHES UP ALL SWITCHES CENTER ALL SWITCHES DOWN VREF
Figure 1. Block Diagram
Pin Description
PIN 1, 2, 11-24, 37-48 3 NAME FUNCTION Signal Termination. Connect to SCSI bus signal lines. Asserting ISO removes the terminators from the R_ _ P, R_ _ N SCSI bus. R_ _ P pins are the ground line for SE operation and the positive lines in differential mode. R_ _ N pins are the signal lines in SE operation and the negative lines in differential mode. TPWR Termination Power. Connect to the SCSI TERMPWR line and decouple with a ceramic 2.2F capacitor. Heat-Sink Ground. Internally connected to the mounting pad. These pins must be connected to ground. These pins should be connected to a ground plane with the layout optimized for heat transfer. Regulator Output Voltage. This must be decoupled with a 4.7F capacitor. Asserting ISO floats this output. A high-frequency capacitor (0.1F) should also be placed on the VREF pin in applications that use fast rise/fall-time drivers. Signal Ground SE Mode Indicator. A high state indicates SE mode detected on SCSI bus. LVD Mode Indicator. A high state indicates LVD mode detected on SCSI. DIFFSENSE Capacitor. Connect a 0.1F capacitor for the DIFFSENSE filter. Input to detect the type of device (differential or single-ended) on the SCSI bus. DIFFSENSE. Output to drive the SCSI bus DIFFSENS line. Isolation Input. When pulled high, terminating resistors and biasing current sources are removed from the SCSI bus. When not connected to ground, the pin has a 10A current source pulling the pin to the high state.
4-9, 28-33
HS_GND
10 25 26 27 34 35 36
VREF GND SE LVD DIFF_CAP DIFFSENS ISO
4
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Ultra3 LVD/SE SCSI 14-Line Terminator DS2127
TPWR 2.2F ISO GND DIFFSENS CONTROL LINES (9) DATA LINES (4) DIFFSENS DIFFSENS TPWR 2.2F ISO GND
VREF DIFF_CAP 4.7F 0.1F 20k 20k
DIFF_CAP VREF 0.1F 4.7F
TPWR DIFF_CAP 2.2F ISO GND VREF DIFFSENS DATA LINES (8) + PARITY DATA LINES (4) + PARITY
DIFF_CAP TPWR 2.2F ISO DIFFSENS GND VREF
4.7F
4.7F
Figure 2. Typical Operating Circuit
Detailed Description
The DS2127 provides dual-mode active terminators with auto-switching SE and LVD termination for 14 SCSI lines. The DIFFSENSE signal performs mode detection and selection. In LVD mode, the termination configuration is a y-type terminator with a 105 differential resistance and a 150 common-mode resistance. The termination resistor is biased with two current sources and the commonmode node is connected to a 1.25V voltage regulator. A fail-safe bias of 112mV is maintained when no drivers are connected to the SCSI bus. In SE mode, each negative signal input pin is connected to 2.85V through a 110 resistor. In HVD mode, the termination resistors are isolated from the SCSI bus and the resistor pins are left floating. The voltage regulator is powered down and the VREF pin is in a high-impedance state. The DIFF_CAP pin is connected to the SCSI DIFFSENSE line and monitors the voltage to determine the proper operating mode of the device. Any DIFFSENSE voltage below 0.5V indicates single ended; any DIFFSENSE voltage between 0.7V and 1.9V is LVD, and above 2.4V is an HVD SCSI. On power-up, the DS2127 assumes SE mode. If the voltage on the DIFF_CAP is between 0.7V and 1.9V, the device waits tDELAY before entering the LVD mode. The delay is the same when changing modes. A new mode change can start at any time after a previous mode change has been detected.
Typically, four DS2127s are used in a SCSI bus segment. On two chips, the DIFF_CAP inputs at each end of the bus should be connected together. There should be a 50Hz noise filter implemented on DIFF_CAP at each end of the bus, as close as possible to the DIFF_CAP pins. This filter consists of a 20k resistor between the DIFFSENS and DIFF_CAP pins, and a 0.1F capacitor from DIFF_CAP to GND. See Figure 2 for the typical operating circuit. When ISO is connected to TPWR, the termination pins are isolated from the SCSI bus and V REF becomes inactive, and the device is in a low-power state. During thermal shutdown, the termination pins are isolated from the SCSI bus and VREF becomes high impedance. The DIFFSENS driver is shut down during either of these two events. LVD and SE signals indicate whether the SCSI bus segment is in LVD or SE mode.
Chip Information
TRANSISTOR COUNT: 8114 CMOS and 87 Bipolar PROCESS: BiCMOS SUBSTRATE CONNECTED TO GROUND
Thermal Information
Thermal Resistance (junction-to-ambient): JA = +29C/W Thermal Resistance (junction-to-case): JC = +10C/W
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5
Ultra3 LVD/SE SCSI 14-Line Terminator DS2127
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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