ST21S07A
SCSI TERMINATOR
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FULLY COMPLIANT WITH SCSI, SCSI-2
AND EMERGING SCSI-E STANDARDS
PROVIDES ACTIVE TERMINATION FOR
NINE SIGNAL LINES
LOW DROPOUT (0.5V) VREGS:2.85V
FACTORY TRIMMED TERMINATION 110Ω
(±2%)
POWER DOWN MODE ISOLATES
TERMINATION RESISTORS FROM THE
BUS
FULLY SUPPORTS ACTIVELY NEGATED
SCSI SIGNALS
COMPATIBLE TO THE DS2107, DS2107A
AND DS21S07
ONBOARD THERMAL SHUTDOWN
CIRCUITRY
AVAILABLE IN SO-16L AND TSSOP20
SCSI BUS HOT PLUG-COMPATIBLE
SOP
DESCRIPTION
The SCSI-2 and SCSI-3 standards recommend
the use of active terminations at both ends of
every cable segment in a SCSI system with a
single-ended drivers and reveivers. The
ST21S07A SCSI terminator, which is fully
TSSOP
compliant with these standands, enables the
designer to gain the benefits of active termination:
greater immunity to voltages drop on the
TERMPWR
(TERMination
PoWeR)
line,
enhanced high level noise immunity, intrinsic
TERMPWR decouplig, and very low quiescent
current consumption.
The ST21S07A integrates a regulator and nine
precise switched 110Ω termination resistors into a
monolithic IC. The ST21S07A can be electrically
isolatesd from the SCSI bus without physical
removal from the SCSI device.
ORDERING CODES
Type
Temperature Range
Package
Comments
ST21S07ACW
ST21S07ACWR
S21S07ACTR (*)
0 to 70 °C
0 to 70 °C
0 to 70 °C
SO-16L (Tube)
SO-16L (Tape & Reel)
TSSOP20 (Tape & Reel)
49parts per tube / 25tube per box
1000 parts per reel
2500 parts per reel
(*) Available on request
February 2001
1/10
ST21S07A
PIN CONFIGURATION
SO-16L
TSSOP20
PIN DESCRIPTION
PlN N°
(TSSP20)
PlN N°
(SO-16L)
1
1
2
3
4
5
6
7
8
2
3
4
5
6
9
7
10
11
8
9
12
2/10
13
14
15
16
17
18
10
11
12
13
14
19
15
20
16
SYMBOL
NAME AND FUNCTION
TERMPWR1 Termination Power 1: Should be connected to the SCSI TERMPWR line.
Must be decoupled with either a 2.2µF or 4.7µF. See Fig. 2.
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
R1
Signal Termination 1: 110 Ω Termination
R2
Signal Termination 2: 110 Ω Termination
R3
Signal Termination 3: 110 Ω Termination
R4
Signal Termination 4: 110 Ω Termination
R5
Signal Termination 5: 110 Ω Termination
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
Reference Voltage 1: Must be external connected directly to the VREF2
VREF1
pin. Must be decoupoled with 4.7µF capacitor as shown in Figure 2
GND
Ground: Signal groud: 0V
TERMPWR Termination Power21: Should be connected to the SCSI TERMPWR line.
Must be decoupled with either a 2.2µF or 4.7µF. See Fig. 2.
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
R6
Signal Termination 6: 110 Ω Termination
R7
Signal Termination 7: 110 Ω Termination
R8
Signal Termination 8: 110 Ω Termination
R9
Signal Termination 9: 110 Ω Termination
NC
Not connected: Do not connect any signal to this pin
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
Reference Voltage 2: Must be external connected directly to the VREF1
VREF2
pin. Must be decoupoled with 4.7µF capacitor
PD
Power Down: When tied low, the ST21S07A enters a power down mode.
Contains an internal 60K pull-up. Strap low to deactivate the ST21S07A,
leave open circuited to activate the ST21S07A
ST21S07A
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
VPIN
Voltage on Any Pin Relative to Ground
Tstg
Storage Temperature Range
Top
Operating Junction Temperature Range
Value
Unit
-1 to 7
V
-55 to +150
°C
0 to +70
°C
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
RECOMMENDED OPERATING CONDITIONS
Symbol
VTP
Parameter
Test Conditions
TERMPWR Voltage
VPDA
PD Active
VPDI
PD Inactive
Min.
Typ.
Max.
Unit
4
5.5
V
-0.3
0.8
V
2
VTP+0.3
V
Typ.
Max.
Unit
1.5
70
250
8
150
mA
mA
µA
112
DC CHARACTERISTICS (T A = 0 to 70°C, unless otherwise specified.)
Symbol
ITP
IPD
Parameter
TERMPWR Current
Power Down Current
Test Conditions
Min.
(note 1, 3)
(note 1, 4)
(note 1, 2, 5)
RTERM
Termination Resistance
(note 1, 2)
108
110
TSD
Die Thermal Shutdown
(note 1, 6)
150
170
CPD
Power Down TermniatioN
Capacitance
Power Down Hysteresis
(note 1, 2, 5, 6)
HPD
3
(note 1)
IIH
Input Leackage High
(note 1, 8)
IIL
Input Leackage Low
(note 1, 7)
Ω
°C
5
280
pF
mV
µA
-1
1
µA
REGULATOR CHARACTERISTICS (TA = 0 to 70°C, unless otherwise specified.)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
2.79
2.85
2.93
V
VREF
Output Voltage
(note 1, 2)
vDROP
Drop-out Voltage
(note 3, 6)
0.3
0.75
V
LIREG
Line Regulation
(note 1, 4)
0.25
2
%
3
LOREG Load Regulatio
(note 1, 2)
0.5
ILIM
Current Limit
(note 1)
450
ISINK
Sink Current
(note 1)
IOUT
Output Current
(note9)
%
mA
200
mA
25.2
mA
Note 1: TERMPWR = 4V to 5.5V
Note2: Signal Lines = 0V to TERMPWR
Note3: All signal lines = 0V
Note 4: All signal lines open
Note 5: PD = 0V
Note 6: Guaranteed by design; not production tested
Note 7: R1 through R9 only
Note 8: R1 through R9 and PD
Note 9: VSIGNAL = 0.2V
3/10
ST21S07A
FUNCTIONAL DESCRIPTION
The ST21S07A consists of a bandgap reference,
buffer amplifier, and nine termination resistors
Figure 1). The bandgap reference circuit produces
a precise 1.25V level which is fed to a buffer
amplifier. The buffer produce a 2.85V level and is
capable of sourcing at least 24mA into each of the
termination resistors when the signal line is low
(active). When the driver for a given signal line
turns off, the terminator will pull the signal line to
2.85V (quiescent state). To handle actively
negated SCSI signals, the buffer can sink 200mA.
When all lines settle in the quiescent state, the
regulator will consume about 1.5mA. When the
ST21S07A is put into power-down mode by
bringing PD low, the power-down circuitry will turn
off the transistors on each signal line. This will
isolated the ST21S07A from the signal lines and
effectively remove it from the circuit. The
Figure 1 : Block Diagram
4/10
power-down pin (PD) has an internal pull-up
resistor.To place the ST21S07A into an active
state, the PD pin should be left open circuited.
To ensure proper operation, both the TERMPWR1
and TERMPWR2 pins must be connected to the
SCSI bus TREMPWR line and both the VREF1
and VREF2 pins must be tied together externally.
Each ST21S07A requires a 4.7µF capacitor
connected between the VREF pins and ground.
Figure 2 details a typical SCSI bus configuration.
In an 8-bit wide SCSI bus arrangement ("A"
Cable), two ST21S07A’s would be needed at each
end of the SCSI cable in order to terminate the 18
active signal lines. In a 16-bit SCSI bus
arrangement ("P" Cable), three ST21S07A’s
would be need at each end of the SCSI cable in
order to terminate the 27 active signal lines.
ST21S07A
Figure 2 : Typical Scsi Bus Configuraion
NOTES:
1) C1 = 4.7µF tantalium C2 = 2.2µF tantalium or 4.7mF aluminum
2) If the ST21S07A is to be embedded into a peripheral that will act as a target on a SCSI bus, it is that recommended TERMPWR be derived
from the SCSI cable, not generated locally. In this configuration, if a power failure occurs in the peripheral, it will not affect the bus.
3) A high frequency bypass capacitor (0.1µF recommended) can be added in parallel to C1 for applications using fast rise/fall time drivers.
5/10
ST21S07A
SO16L MECHANICAL DATA
mm
DIM.
MIN.
TYP.
A
a1
inch
MAX.
MIN.
TYP.
2.65
0.1
0.104
0.2
a2
MAX.
0.004
0.008
2.45
0.096
b
0.35
0.49
0.014
0.019
b1
0.23
0.32
0.009
0.012
C
0.5
0.020
c1
45 (typ.)
D
10.1
10.5
0.397
0.413
E
10.0
10.65
0.3.93
0.419
e
1.27
0.050
e3
8.89
0.350
F
7.4
7.6
0.291
0.300
L
0.5
1.27
0.020
0.050
M
S
0.75
0.029
8 (max.)
P013I
6/10
ST21S07A
TSSOP20 MECHANICAL DATA
mm
DIM.
MIN.
inch
TYP.
MAX.
A
MIN.
TYP.
MAX.
1.1
0.433
A1
0.05
0.10
0.15
0.002
0.004
0.006
A2
0.85
0.9
0.95
0.335
0.354
0.374
b
0.19
0.30
0.0075
0.0118
c
0.09
0.2
0.0035
0.0079
D
6.4
6.5
6.6
0.252
0.256
0.260
E
6.25
6.4
6.5
0.246
0.252
0.256
E1
4.3
4.4
4.48
0.169
0.173
0.176
e
0.65 BSC
0.0256 BSC
K
0o
4o
8o
0o
4o
8o
L
0.50
0.60
0.70
0.020
0.024
0.028
A
A2
A1
b
K
e
L
E
c
D
E1
PIN 1 IDENTIFICATION
1
7/10
ST21S07A
8/10
ST21S07A
9/10
ST21S07A
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the
consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from
its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications
mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information
previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or
systems without express written approval of STMicroelectronics.
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