Rainbow Electronics DS2127 User Manual
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 110Ω resistors
and one regulator for active-negation bias.
Applications
SCSI Array Backplane
SCSI Cables
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
Ultra3 LVD/SE SCSI 14-Line Terminator
______________________________________________ Maxim Integrated Products 1
R13N
R13P
R12N
R12P
R11N
R11P
R10N
R10P
R9N
R9P
R8N
R8P
R2P
R2N
R3P
R3N
R4P
R4N
R5P
R5N
R6P
R6N
R7P
R7N
13
14
15
16
17
18
19
20
21
22
23
24
48
47
46
45
44
43
42
41
40
39
38
37
LQFP
GND
SE
LVD
HS_GND
HS_GND
HS_GND
HS_GND
HS_GND
HS_GND
DIFF_CAP
DIFFSENS
ISO
2526272829303132333435
36
12111098765432
1
R1N
R1P
V
REF
HS_GND
HS_GND
HS_GND
HS_GND
HS_GND
HS_GND
TPWR
R14N
R14P
DS2127
TOP VIEW
Pin Configuration
Ordering Information
Rev 0; 7/03
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.
PART
TEMP RANGE
PINPACKAGE
TOP
MARK
DS2127 0°C to +70°C 48 LQFP
DS2127
DS2127
Ultra3 LVD/SE SCSI 14-Line Terminator
2 _____________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(TPWR = V
TPWR(MIN)
to V
TPWR(MAX)
, TA= 0°C to +70°C, unless otherwise noted.)
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.
Voltage Range on All Pins Relative to Ground ......-0.3V to +6.0V
V
REF
Continuous Output Current....................................±200mA
Operating Temperature Range...............................0°C to +70°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Soldering Temperature .......................................See IPC/JEDEC
J-STD-020A Specification
PARAMETER
SYMBOL
CONDITIONS MIN
TYP
MAX
UNITS
LVD 2.7 3.3 5.5
TPWR Operating Supply Range
(Note 1)
V
TPWR
SE 4 5.0 5.5
V
TPWR SUPPLY CURRENT
LVD SCSI mode 32
SE SCSI mode 10
mA
TPWR Supply Current (All Lines
Open)
ISO mode (terminators disabled)
µA
LVD TERMINATION (Applies to each line pair, 1 to 14 in LVD mode)
Differential-Mode Termination
Resistance
R
DM
100
Ω
Common-Mode Termination
Resistance
R
CM
RP and RN shorted together
(V
CM(MAX)
= 2V, V
CM(MIN)
= 0.5V)
110
Ω
Differential-Mode Bias V
DM
All lines open 100
mV
Common-Mode Bias V
CM
RP and RN shorted together (Note 1)
V
SE TERMINATION (Applies to single-ended terminators, 1 to 14 in SE mode)
Single-Ended Mode Termination
Resistance
R
SE
RSE = (VLX - 0.2) / ILX, where VLX = voltage
at terminator pin with pin unloaded and
I
LX
= current for each terminator pin with
the pin forced to 0.2V
110
Ω
Signal level at 0.2V, all lines low -21 -24
Termination Current I
SE
Signal level at 0.5V -18
mA
SE Voltage Reference V
REF
2.7
V
Pin Leakage With ISO high
nA
Single-Ended GND Resistance R
GND
Measured at RP pins, I = 10mA 20 60 Ω
TERMINATOR PIN CAPACITANCE
Terminator Pin Capacitance C
IN
With ISO high (Note 2) 3 pF
V
REF
REGULATOR
1.25V Regulator Output Voltage
0.5V ≤ V
CM
≤ 2.0V, VCM applied to all R
P
and RN lines simultaneously
V
1.25V Regulator Short-Circuit
Source Current
V
REF
= 0V
mA
1.25V Regulator Short-Circuit
Sink Current
I
SINK
V
REF
= 3.3V 170 300
mA
I
TPWR_LVD
I
TPWR_SE
I
TPWR_ISO
750
V
REF_LVD
I
SOURCE
110
165
125
115.5
-25.4
-22.4
2.85 3.0
400
1.15 1.25 1.35
104.5
1.15 1.25 1.35
-375 -700 -1000
700
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