18-Bit Switchable Active SCSI-2 Bus Terminator (110 W)With Voltage Regulator

MCCS142236
18-Bit Switchable Active
SCSI-2 Bus Terminator
(110Ω)
With Voltage Regulator
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The MCCS142236 is a precision 18−bit switchable active SCSI−2
bus terminator with an on−board 2.85V regulator. When the
Disconnect pin is LOW according to the truth table below, the
MCCS142236 provides 110Ω ±5% precision resistor pull−ups to a
2.85V reference for termination of 18−bits in a SCSI−2 standard bus
system interface.
When the Disconnect pin is HIGH, the device outputs are in the high
impedance state on all 18 bits. The regulator is also turned off, greatly
reducing standby power. Even with no Termpwr applied, the outputs
remain in the high impedance state.
18−BIT SWITCHABLE
ACTIVE SCSI−2
BUS TERMINATOR
• Complies With SCSI and SCSI−2 Standards
• Pin Compatible With UC5601, UC5602 and UC5608
• For Opposite Disconnect Polarity See ON Semiconductor’s
•
•
•
•
•
•
•
•
DW SUFFIX
28−LEAD SOIC WIDE
CASE 751F−05
MCCS142238
18 Switchable 110Ω Terminating Resistors
4pF Channel Capacitance During Disconnect
Fully Supports Active Negation (Sinks Minimum of 220mA)
Built−In 2.85V Regulator With Low Dropout Voltage
Very Low Supply Current When Resistors Are Disabled (30μA Max)
−650mA Source Current
Thermal Shutdown Protection
Thin Profile Surface Mount Package: 28−Lead SOIC
The regulator has a guaranteed dropout voltage of less than 900mV, allowing regulation of supply voltages less than 4.0V.
The MCCS142236 is protected by thermal shutdown. Other features include low disconnect current (30μA), over 220mA of
active negation current sink capability, and 4pF disconnect capacitance.
In 8−bit SCSI applications (“A” cable), only one MCCS142236 is needed at each end of the SCSI cable in order to terminate
the 18 active signal lines. In 16−bit WIDE SCSI applications (“P” cable), either two MCCS142236s, one each of the
MCCS142236 and MCCS142237, or three MCCS142237s would be needed at each end of the SCSI cable in order to properly
terminate the 27 active signal lines. The MCCS142237 is a 9−bit version of the MCCS142236.
For information on “Power Dissipation for Active SCSI Terminators,” refer to ON Semiconductor Application Note
AN1408/D, available through ON Semiconductor Fax System, or through the ON Semiconductor Literature Distribution
Center.
TRUTH TABLE
© Semiconductor Components Industries, LLC, 2010
February, 2010 − Rev. 6
Disconnect
Output
0
Terminated
1
Z
1
Publication Order Number:
MCCS142236/D
MCCS142236
Disconnect
1
28
GND
Line1
2
27
Line18
Line2
3
26
Line17
Line3
4
25
Line16
Line4
5
24
Line15
Line5
6
23
Line14
GND*
7
22
GND*
GND*
8
21
GND*
GND*
9
20
GND*
Line6
10
19
Line13
Line7
11
18
Line12
Line8
12
17
Line11
Line9
13
16
Line10
Termpwr
14
15
Reg
MCCS142236
* Pins 7, 8, 9, 20, 21 and 22 are heat-sink grounds.
Pin 28 is the signal ground.
Figure 1. 28−Lead Pinout (Top View)
Disconnect Input Application
Result
A. No Connection to Disconnect
Disconnect input will be pulled “HIGH” internally, causing all outputs to
be high impedance.
B. Single Pole Switch to GND
Disconnect input will be pulled “HIGH” internally when the switch is
open, causing all outputs to be high impedance.
Disconnect input will be held “LOW” when the switch is closed,
providing 110Ω impedance to each of the bus lines.
C. Double Pole Switch Between
Supply and GND
This is a more expensive way to accomplish application B above. It is
more economical to allow the internal pullup to provide the “HIGH” input
level. The supply source in this case could be Termpwr or VCC.
D. Hardwired “High”
The MCCS142236 will be permanently disconnected causing all
outputs to be high impedance.
E. Hardwired “Low”
The MCCS142236 will be permanently connected providing 110Ω
impedance to each of the bus lines.
MAXIMUM RATINGS*
Symbol
Parameter
Value
Unit
Termpwr
DC Supply Voltage
7.0
V
VLine
Signal Line Voltage
−1.0 to +7.0
V
IREG
Regulator Current
tstg
Storage Temperature Range
1
A
−65 to +150
°C
* Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the
Recommended Operating Conditions.
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2
MCCS142236
RECOMMENDED OPERATING CONDITIONS
Symbol
Parameter
Min
Max
Unit
3.8
5.25
V
DC Input Voltage (Disconnect Pin)
0
Termpwr
V
VLine
Signal Line Voltage
0
5.0
V
TA
Operating Temperature Range
0
+70
°C
tr, tf
Input Rise/Fall Time
0
500
ns
Termpwr
DC Supply Voltage
Vin
ELECTRICAL CHARACTERISTICS (Unless otherwise stated, these specifications apply for TA = 0° to 70°C,
Termpwr = 4.75V, Disconnect = Ground)
Symbol
Characteristic
Min
Typ
Max
Unit
Condition
Supply Current Section
ITermpwr
Termpwr Supply Current
15
410
27
465
mA
All Termination Lines = Open
All Termination Lines = 0.5V
Ipd
Power Down Mode Current
10
30
μA
Disconnect = Open
104.5
110.0
115.5
Ω
2.8
2.85
3.0
V
−24
mA
Signal Line = 0.5V
1
μA
Termpwr = 5.25V,
Reg = Open, Disconnect = 4V
4.0
5.0
pF
Disconnect = Open
2.85
3.0
V
Signal Lines = 0V or 4V
Output Section (Termination Lines)
R110
Termination Impedance
VOH
Output HIGH Voltage
Isource
Source Current Capability per Line
IOZ
Output Leakage Current
Signal Lines = 0 to 5.25V
CO
Output Capacitance (Note 2.)
−19.9
Note 1.
Regulator Section
VReg
Regulator Voltage
Linereg
Line Regulation
27
40
mV
Signal Lines Open,
Termpwr = 4V to 6V
Loadreg
Load Regulation
35
60
mV
Signal Lines = 0V to 3V
VDO
Drop Out Voltage
0.7
0.9
V
ILim
Current Limit
−450
−650
−850
mA
Reg = 0V
Isink
Current Sink Capability
220
350
400
mA
Reg = 3.5V
Tshut
Thermal Shutdown
2.8
150
Signal Lines = 0.5V
°C
Disconnect Section
DTH
Disconnect Threshold (Note 2.)
IIL
Input Leakage Current
1.1
1.3
1.7
V
100
120
μA
Disconnect = 0V
1. Measured with one output high and all other signal lines open.
2. Not production tested, guaranteed by design.
AC CHARACTERISTICS (Note 3., Reg = 2.85, CL = 2.2μF, tr = tf = 6ns)
Symbol
Parameters
0°C to + 70°C
Unit
t(connect)
Max Connect Time, High Impedance to Termination, Disconnect to Outputs
100
μs
t(disconnect)
Max Disconnect Time, Termination to High Impedance, Disconnect to Outputs
20
μs
3. Not production tested, guaranteed by design.
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3
MCCS142236
Termpwr
Reg
110Ω
+
Voltage
Reference
−
50kΩ
Line 1
Shunt
Control
110Ω
Thermal
Shutdown
Line 18
Enable
Logic
Disconnect
Charge
Pump
PATENTED CIRCUIT
DESIGN
Figure 2. MCCS142236 Block Diagram
2.2μF
2.2μF
Termpwr
Termpwr
Reg
Reg
2.2μF
Disconnect
MCCS142236
Line 18
2.2μF
0.1μF
Disconnect
0.1μF
Line 1
MCCS142236
Line 1
Line 18
TO
RECEIVERS
TO
RECEIVERS
BUS DRIVER
BUS DRIVER
TO
RECEIVERS
TO
RECEIVERS
BUS DRIVER
BUS DRIVER
SCSI
CABLE
Figure 3. Typical SCSI Bus Configuration Using the MCCS142236
30Ω
Terminated
Reg
80Ω
Output
High Impedance
4.0pF
Figure 4. Output Impedance Model
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4
MCCS142236
PACKAGE DIMENSIONS
DW SUFFIX
PLASTIC SOIC PACKAGE
CASE 751F−05
ISSUE G
−X−
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS D AND E DO NOT INCLUDE MOLD
PROTRUSION
4. MAXIMUM MOLD PROTRUSION 0.15 PER SIDE.
5. DIMENSION B DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBER
PR5OTRUSION SHALL NOT BE 0.13 TOTATL IN
EXCESS OF B DIMENSION AT MAXIMUM
MATERIAL CONDITION.
D
28
15
H
E
0.25
M
Y
M
−Y−
1
DIM
A
A1
B
C
D
E
G
H
L
M
14
PIN 1 IDENT
A
L
0.10
G
B
0.025
M
T X
S
A1
Y
−T−
SEATING
PLANE
MILLIMETERS
MIN
MAX
2.35
2.65
0.13
0.29
0.35
0.49
0.23
0.32
17.80
18.05
7.40
7.60
1.27 BSC
10.05
10.55
0.41
0.90
0_
8_
C
M
S
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
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“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
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MCCS142236/D
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