MAXIM DS2127

Rev 1; 3/04
Ultra3 LVD/SE SCSI 14-Line Terminator
Features
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.
♦ 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
Ordering Information
Applications
SCSI Array Backplane
SCSI Cables
PART
TEMP RANGE
DS2127
0°C to +70°C
PINPACKAGE
TOP
MARK
48 LQFP
DS2127
Pin Configuration
1
2
3
HS_GND
HS_GND
TPWR
R14N
R14P
4
5
6
7
HS_GND
HS_GND
HS_GND
HS_GND
8
9
10
R1N
R1P
VREF
11
12
TOP VIEW
R2P
R2N
R3P
R3N
R4P
13
48
14
47
15
46
16
45
17
44
R4N
R5P
R5N
R6P
R6N
R7P
R7N
18
43
19
42
DS2127
36
ISO
34
33
32
31
30
35
GND
SE
LVD
29
37
28
38
24
27
39
23
HS_GND
HS_GND
HS_GND
HS_GND
HS_GND
HS_GND
DIFF_CAP
DIFFSENS
40
22
26
41
21
25
20
R13N
R13P
R12N
R12P
R11N
R11P
R10N
R10P
R9N
R9P
R8N
R8P
LQFP
______________________________________________ Maxim Integrated Products
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.
1
DS2127
General Description
DS2127
Ultra3 LVD/SE SCSI 14-Line Terminator
ABSOLUTE MAXIMUM RATINGS
Voltage Range on All Pins Relative to Ground ......-0.3V to +6.0V
VREF 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
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 = 0°C to +70°C, unless otherwise noted.)
PARAMETER
SYMBOL
TPWR Operating Supply Range
(Note 1)
VTPWR
CONDITIONS
LVD
SE
MIN
TYP
MAX
2.7
3.3
5.5
4
5.0
5.5
UNITS
V
TPWR SUPPLY CURRENT
TPWR Supply Current (All Lines
Open)
ITPWR_LVD LVD SCSI mode
32
mA
ITPWR_SE
SE SCSI mode
10
ITPWR_ISO
ISO mode (terminators disabled)
750
µA
100
110
Ω
110
165
Ω
LVD TERMINATION (Applies to each line pair, 1 to 14 in LVD mode)
Differential-Mode Termination
Resistance
RDM
Common-Mode Termination
Resistance
RCM
RP and RN shorted together
(VCM(MAX) = 2V, VCM(MIN) = 0.5V)
Differential-Mode Bias
VDM
All lines open
100
125
mV
Common-Mode Bias
VCM
RP and RN shorted together (Note 1)
1.15
1.25
1.35
V
104.5
110
115.5
Ω
Signal level at 0.2V, all lines low
-21
-24
Signal level at 0.5V
-18
SE TERMINATION (Applies to single-ended terminators, 1 to 14 in SE mode)
Single-Ended Mode Termination
Resistance
RSE
Termination Current
ISE
SE Voltage Reference
VREF
Pin Leakage
Single-Ended GND 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
2.7
2.85
With ISO high
RGND
Measured at RP pins, I = 10mA
-25.4
-22.4
20
mA
3.0
V
400
nA
60
Ω
3
pF
TERMINATOR PIN CAPACITANCE
Terminator Pin Capacitance
CIN
With ISO high (Note 2)
VREF REGULATOR
1.25V Regulator Output Voltage
VREF_LVD
0.5V ≤ VCM ≤ 2.0V, VCM applied to all RP
and RN lines simultaneously
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
2
_____________________________________________________________________
Ultra3 LVD/SE SCSI 14-Line Terminator
(TPWR = VTPWR(MIN) to VTPWR(MAX), TA = 0°C to +70°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
1.0
2.5
%
2.7
2.85
3.0
V
VREF REGULATOR
VREF unloaded; vary TPWR from
2.7V to 5.5V
1.25V Regulator Line Regulation
2.85V Regulator
2.85V Regulator Short-Circuit
Source Current
VREF = 0V
-375
-700
-1000
mA
2.85V Regulator Short-Circuit
Sink Current
VREF = 3.3V
170
300
700
mA
2.85V Regulator Line Regulation
VREF unloaded; vary TPWR from
2.7V to 5.5V
1.0
2.5
%
DIFFSENS OUTPUT
DIFFSENS Driver Output Voltage
VDSO
-5mA ≤ IDIFFSENS ≤ 50µA
1.2
1.4
V
DIFFSENS Driver Source Current
IDSH
VDIFFSENS = 0V
-15
-5
mA
IDSL
VDIFFSENS = 2.75V
100
200
µA
With ISO high, |VDIFFSENS| = 0.3V
-3
+1
With ISO high, |VDIFFSENS - VTPWR| = 0.3V
1
3
DIFFSENS Driver Sink Current
ILEAK,
DIFFSENS Leakage (Note 3)
LOW
ILEAK,
HIGH
µA
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
For increasing temperature
Thermal-Shutdown Hysteresis
130
°C
10
°C
MODE CHANGE DELAY/FILTER
Mode Change Delay
tDELAY
0.66
Input Low Voltage
VIL
Input High Voltage
VIH
Input Current
IIL
1.25
2.00
ms
-0.3
+0.8
V
2.0
TPWR + 0.3
LOGICAL SIGNALS (ISO)
V
VCC = 3.3V
-30
-10
µA
STATUS BITS (LVD, SE)
Source Current
IOH
VCC = 3.3V, VLOAD = 2.4V
-4
-6
mA
Sink Current
IOL
VCC = 3.3V, VLOAD = 0.4V
2
5
mA
IL
VIL = -0.3V
DIFF_CAP
Input Current
-1
+1
µA
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
DIFF_CAP SE Operating Range
VTPWR + 0.3
V
Note 1: All voltages are referenced to ground.
Note 2: Guaranteed by design and not production tested.
Note 3: Room temperature only.
_____________________________________________________________________
3
DS2127
ELECTRICAL CHARACTERISTICS (continued)
DS2127
Ultra3 LVD/SE SCSI 14-Line Terminator
2.15V
DELAY/
FILTER
DIFF_CAP
LVD
HVD
0.6V
LVD
LVD
SE
SE
SE
LVD SE HVD
THERMAL
SHUTDOWN
ISO
1.30V
DIFFSENS
10µA
110Ω
CONTROL LOGIC
52Ω
DS2127
R1N
124Ω
BANDGAP
REFGEN AND
TRIM
1.25V
(LVD)
SE
HVD/ISO
LVD
R1P
52Ω
2.15V
1.30V
0.6V
110Ω
2.85V
(SE)
52Ω
R14N
124Ω
ALL SWITCHES UP
ALL SWITCHES CENTER
ALL SWITCHES DOWN
52Ω
R14P
VREF
Figure 1. Block Diagram
Pin Description
PIN
1, 2, 11–24,
37–48
4
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.
3
TPWR
4–9, 28–33
HS_GND
10
VREF
25
GND
26
SE
27
LVD
Termination Power. Connect to the SCSI TERMPWR line and decouple with a ceramic
2.2µF 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 4.7µF capacitor. Asserting ISO floats this
output. A high-frequency capacitor (0.1µF) 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.
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
DIFFSENS
DIFFSENSE. Output to drive the SCSI bus DIFFSENS line.
36
ISO
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 10µA current source pulling the pin to the
high state.
_____________________________________________________________________
Ultra3 LVD/SE SCSI 14-Line Terminator
DIFFSENS
DIFFSENS
0.1µF
20kΩ
20kΩ
4.7µF
0.1µF
DIFF_CAP TPWR
2.2µF
DATA LINES (8) + PARITY
DATA LINES (4) + PARITY
ISO
GND
VREF
GND
DIFF_CAP VREF
TPWR DIFF_CAP
2.2µF
ISO
DIFFSENS
VREF DIFF_CAP
4.7µF
2.2µF
CONTROL LINES (9)
DATA LINES (4)
ISO
GND
DS2127
TPWR
TPWR
2.2µF
DIFFSENS
4.7µF
ISO
DIFFSENS
GND
VREF
4.7µF
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 105Ω differential resistance and a
150Ω 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 110Ω 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 20kΩ resistor
between the DIFFSENS and DIFF_CAP pins, and a
0.1µF 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):
θJA = +29°C/W
Thermal Resistance (junction-to-case):
θJC = +10°C/W
_____________________________________________________________________
5
DS2127
Ultra3 LVD/SE SCSI 14-Line Terminator
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.
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© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.