MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
9-Bit Switchable Active
SCSI-2 Bus Terminator (110
Ω
)
With Voltage Regulator
The MCCS142237™ is a precision 9–bit switchable active SCSI–2 bus
terminator with an on–board 2.85V regulator. The SCSI–2 standard
recommends the use of active terminations at both ends of every cable
segment in a SCSI system with single–ended drivers and receivers. The
MCCS142237 enables the designer to gain the benefits of active
termination: greater immunity to voltage drops on the TERMPWR
(TERMination PoWeR) line, enhanced high–level immunity, intrinsic
TERMPWR decoupling, and very low quiescent current consumption.
When the device is enabled (PD = HIGH), the MCCS142237 provides
110Ω precision resistor pull–ups to a 2.85V reference for termination of
9–bits in a SCSI–2 standard bus system interface. When PD is LOW, the
device is in the High Impedance State on all 9 bits.
MCCS142237
9–BIT SWITCHABLE
ACTIVE SCSI–2
BUS TERMINATOR
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Complies With SCSI and SCSI–2 Standards
Pin Compatible With DS2107, DS2107A and DS21S07A
9 Switchable 110Ω Terminating Resistors
Power–Down Mode Disengages Terminating Resistors
Built–In 2.85V Regulator
Guaranteed Maximum 1.0V Dropout Voltage
3pF Channel Capacitance During “Power–Down”
Thermal Shutdown Circuitry
Fully Supports Active Negation SCSI Signals
Regulator Short Circuit Protection
Thin Profile 20–Pin TSSOP and 16–Pin SOIC Packages
TRUTH TABLE
PD
Output
DT SUFFIX
20–LEAD PLASTIC TSSOP PACKAGE
CASE 948D–03
DW SUFFIX
16–LEAD WIDE SOIC PACKAGE
CASE 751G–02
The regulator has a dropout voltage of less than 1.0V, allowing
regulation of input voltages less than 4.0V. Internal protective features
include thermal shutdown.
The regulator produces a 2.85V level and is capable of sourcing 24mA
0
Z
into each of the termination resistors when the signal line is low
(asserted). When the driver for a given signal line turns off, the terminator
1
Terminated
will pull the signal line to 2.85V (quiescent state). To handle actively
negated SCSI signals, the regulator can sink over 220mA. When the
Power–Down pin (PD) is LOW, the power–down circuitry will turn off the transistors on each signal line. This isolates the
MCCS142237 from the signal lines and effectively removes it from the bus. The PD pin has an internal pull–up resistor. To place
the terminator into the active state, the PD pin should either be left open circuited or tied HIGH.
To ensure proper operation, both the TERMPWR1 and TERMPWR2 pins must be connected to the SCSI bus TERMPWR line
and both the VREF1 and VREF2 pins must be tied together externally. Each MCCS142237 requires a minimum 2.2µF capacitor
connected between the VREF pins and ground.
In 8–bit SCSI applications (“A” cable), two MCCS142237s are 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), three MCCS142237s would be needed at each end of the
SCSI cable in order to terminate the 27 active signal lines.
For information on “Power Dissipation for Active SCSI Terminators,” refer to Motorola Application Note AN1408/D, available
through the Motorola Design–NET Fax System, or through the Motorola Literature Distribution Center.
MCCS and Mfax are trademarks of Motorola, Inc.
1/97
©
Motorola, Inc. 1997
1
REV 5
MCCS142237
TERMPWR1 1
HS–GND 2
R1 3
R2 4
R3 5
R4 6
R5 7
HS–GND 8
VREF1 9
GND 10
20 PD
19 VREF2
18 HS–GND
17 NC
16 R9
15 R8
14 R7
13 R6
12 HS–GND
11 TERMPWR2
TERMPWR1 1
R1 2
R2 3
R3 4
R4 5
R5 6
VREF1 7
GND 8
16 PD
15 VREF2
14 NC
13 R9
12 R8
11 R7
10 R6
9 TERMPWR2
Figure 1. 20–Lead Pinout
(Top View)
PIN DESCRIPTIONS
Symbol
TERMPWR1
R1
R2
R3
R4
R5
VREF1
GND
TERMPWR2
R6
R7
R8
R9
NC
VREF2
PD
20–Lead
TSSOP
1
3
4
5
6
7
9
10
11
13
14
15
16
17
19
20
16–Lead
SOIC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Figure 2. 16–Lead Pinout
(Top View)
Description
Termination Power 1.
Connect to the SCSI TERMPWR line. See Figure 4.
Signal Termination 1.
110 ohm termination.
Signal Termination 2.
110 ohm termination.
Signal Termination 3.
110 ohm termination.
Signal Termination 4.
110 ohm termination.
Signal Termination 5.
110 ohm termination.
Reference Voltage 1.
Must be externally connected directly to the VREF2 pin. See Figure 4.
Ground.
Signal ground; 0.0V.
Termination Power 2.
Should be connected to the SCSI TERMPWR line. See Figure 4.
Signal Termination 6.
110 ohm termination.
Signal Termination 7.
110 ohm termination.
Signal Termination 8.
110 ohm termination.
Signal Termination 9.
110 ohm termination.
No Connect.
Do not connect any signal to this pin.
Reference Voltage 2.
Must be externally connected directly to the VREF1 pin. See Figure 4.
Power Down.
When tied low, the MCCS142237 enters power– down mode. Contains an inter-
nal 50kΩ pull–up. Tie low to de–activate the MCCS142237, leave open circuited or tie high to
activate the MCCS142237.
Heat Sink Ground.
HS–GND
2,8,12,18
N/A
PD Input Application
A. No Connection to PD
B. Single Pole Switch to GND
Result
PD input will be pulled “HIGH” internally. This connects the termination resistors.
PD input will be pulled “HIGH” internally when the switch is open, which connects the
termination resistors. PD input will be held “LOW” when the switch is closed,
disconnecting the termination resistors and turning off the voltage regulator.
The MCCS142237 will be permanently connected and provide termination on all outputs.
The MCCS142237 will be permanently disconnected.
C. Hardwired “High”
D. Hardwired “Low”
MOTOROLA
2
SCSI TERMINATORS
BR1486
MCCS142237
MAXIMUM RATINGS*
Symbol
TERMPWR
VLine
IReg
tstg
VREF
DC Supply Voltage
Voltage on Any Pin Relative to Ground
Regulator Output Current
Storage Temperature Range
Reference Voltage
Parameter
Value
7.0
–1.0 to +7.0
0.5
–65 to +150
5.0
Unit
V
V
A
°C
V
* Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the
Recommended Operating Conditions.
RECOMMENDED OPERATING CONDITIONS
(0° to 70°C)
Symbol
VTP
VPDA
VPDI
VLine
TA
TERMPWR Voltage
PD Active
PD Inactive
Signal Line Voltage
Operating Temperature Range
2.0
0
0
Parameter
Min
3.9
Max
5.25
0.8
VTP + 0.3
3.0
70
Unit
V
V
V
V
°C
DC CHARACTERISTICS
(0° to 70°C)
Symbol
ITP
IPD
RTERM
TSD
CPD
HPD
IIH
IIL
Characteristic
TERMPWR Current
5
Power–Down Current
Termination Resistance
Die Thermal Shutdown
Power–Down Termination Capacitance
PD Hysteresis
Input Leakage HIGH
Input Leakage LOW
–1.0
1.0
104.5
100
110
150
3
280
4.5
115.5
Min
Typ
Max
250
10
Unit
mA
µA
Ω
°C
pF
mV
µA
µA
Condition
4V < TERMPWR < 5.25V (Note 1.)
4V < TERMPWR < 5.25V (Note 2.)
4V < TERMPWR < 5.25V (Note 4.)
4V < TERMPWR < 5.25V
4V < TERMPWR < 5.25V
4V < TERMPWR < 5.25V (Notes 3., 4.)
4V < TERMPWR < 5.25V
4V < TERMPWR < 5.25V (Notes 4., 5.)
4V < TERMPWR < 5.25V (Notes 4., 5.)
1. All signal lines = 0.0V
2. All signal lines open
3. Guaranteed by characterization; not production tested
4. PD = 0.0V
5. Resistors Only
REGULATOR CHARACTERISTICS
(0° to 70°C)
Symbol
VREF
VDROP
LIReg
LOReg
ILim
ISink
Characteristic
Reference Voltage
Drop Out Voltage
Line Regulation
Load Regulation
Current Limit
Sink Current
–300
220
Min
2.79
Typ
2.85
0.75
<1.0
<1.0
–350
300
Max
2.91
1.00
2.0
3.0
–400
400
Unit
V
V
%
%
mA
mA
Condition
4V < TERMPWR < 5.25V (Notes 6., 8.)
Notes 6., 7.
4V < TERMPWR < 5.25V (Note 8.)
4V < TERMPWR < 5.25V
4V < TERMPWR < 5.25V (Note 9.)
4V < TERMPWR < 5.25V (Note 10.)
6. All signal lines = 0.0V
7. Guaranteed by design; not production tested
8. All signal lines open
9. VREF pins = 0V
10. VREF pins = 3.5V
SCSI TERMINATORS
BR1486
3
MOTOROLA
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