1/10
February 2001
s
FULLY COMPLIANT WITH SCSI, SCSI-2
AND EMERGING SCSI-E STANDARDS
s
PROVIDES ACTIVE TERMINATION FOR
NINE SIGNAL LINES
s
LOW DROPOUT (0.5V) VREGS:2.85V
s
FACTORY TRIMMED TERMINATION 110
(
2%)
s
POWER DOWN MODE ISOLATES
TERMINATION RESISTORS FROM THE
BUS
s
FULLY SUPPORTS ACTIVELY NEGATED
SCSI SIGNALS
s
COMPATIBLE TO THE DS2107, DS2107A
AND DS21S07
s
ONBOARD THERMAL SHUTDOWN
CIRCUITRY
s
AVAILABLE IN SO-16L AND TSSOP20
s
SCSI BUS HOT PLUG-COMPATIBLE
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
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 110
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
(*) Available on request
Type
Temperature Range
Package
Comments
ST21S07ACW
0 to 70 C
SO-16L (Tube)
49parts per tube / 25tube per box
ST21S07ACWR
0 to 70 C
SO-16L (Tape & Reel)
1000 parts per reel
S21S07ACTR (*)
0 to 70 C
TSSOP20 (Tape & Reel)
2500 parts per reel
ST21S07A
SCSI TERMINATOR
SOP
TSSOP
ST21S07A
2/10
PIN CONFIGURATION
PIN DESCRIPTION
PlN N
(TSSP20)
PlN N
(SO-16L)
SYMBOL
NAME AND FUNCTION
1
1
TERMPWR1 Termination Power 1: Should be connected to the SCSI TERMPWR line.
Must be decoupled with either a 2.2
F or 4.7
F. See Fig. 2.
2
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
3
2
R1
Signal Termination 1: 110
Termination
4
3
R2
Signal Termination 2: 110
Termination
5
4
R3
Signal Termination 3: 110
Termination
6
5
R4
Signal Termination 4: 110
Termination
7
6
R5
Signal Termination 5: 110
Termination
8
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
9
7
V
REF1
Reference Voltage 1: Must be external connected directly to the V
REF2
pin. Must be decoupoled with 4.7
F capacitor as shown in Figure 2
10
8
GND
Ground: Signal groud: 0V
11
9
TERMPWR
Termination Power21: Should be connected to the SCSI TERMPWR line.
Must be decoupled with either a 2.2
F or 4.7
F. See Fig. 2.
12
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
13
10
R6
Signal Termination 6: 110
Termination
14
11
R7
Signal Termination 7: 110
Termination
15
12
R8
Signal Termination 8: 110
Termination
16
13
R9
Signal Termination 9: 110
Termination
17
14
NC
Not connected: Do not connect any signal to this pin
18
HS-GND
Heat Sink Ground: Internally connected to the mounting pad. Should be
either grounded or electrically isolated from the other circuitry.
19
15
V
REF2
Reference Voltage 2: Must be external connected directly to the V
REF1
pin. Must be decoupoled with 4.7
F capacitor
20
16
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
SO-16L
TSSOP20
ST21S07A
3/10
ABSOLUTE MAXIMUM RATINGS
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
DC CHARACTERISTICS (T
A
= 0 to 70C, unless otherwise specified.)
REGULATOR CHARACTERISTICS (T
A
= 0 to 70C, unless otherwise specified.)
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: R
1
through R
9
only
Note 8: R
1
through R
9
and PD
Note 9: V
SIGNAL
= 0.2V
Symbol
Parameter
Value
Unit
V
PIN
Voltage on Any Pin Relative to Ground
-1 to 7
V
T
stg
Storage Temperature Range
-55 to +150
C
T
op
Operating Junction Temperature Range
0 to +70
C
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
TP
TERMPWR Voltage
4
5.5
V
V
PDA
PD Active
-0.3
0.8
V
V
PDI
PD Inactive
2
V
TP
+0.3
V
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
I
TP
TERMPWR Current
(note 1, 3)
(note 1, 4)
1.5
250
8
mA
mA
I
PD
Power Down Current
(note 1, 2, 5)
70
150
A
R
TERM
Termination Resistance
(note 1, 2)
108
110
112
T
SD
Die Thermal Shutdown
(note 1, 6)
150
170
C
C
PD
Power Down TermniatioN
Capacitance
(note 1, 2, 5, 6)
3
5
pF
H
PD
Power Down Hysteresis
(note 1)
280
mV
I
IH
Input Leackage High
(note 1, 8)
-1
A
I
IL
Input Leackage Low
(note 1, 7)
1
A
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
REF
Output Voltage
(note 1, 2)
2.79
2.85
2.93
V
v
DROP
Drop-out Voltage
(note 3, 6)
0.3
0.75
V
LI
REG
Line Regulation
(note 1, 4)
0.25
2
%
LO
REG
Load Regulatio
(note 1, 2)
0.5
3
%
I
LIM
Current Limit
(note 1)
450
mA
I
SINK
Sink Current
(note 1)
200
mA
I
OUT
Output Current
(note9)
25.2
mA
ST21S07A
4/10
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
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 4.7
F 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.
Figure 1 : Block Diagram
ST21S07A
5/10
Figure 2 : Typical Scsi Bus Configuraion
NOTES:
1) C
1
= 4.7
F tantalium C
2
= 2.2
F 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 (0.1
F recommended) can be added in parallel to C1 for applications using fast rise/fall time drivers.
ST21S07A
6/10
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
2.65
0.104
a1
0.1
0.2
0.004
0.008
a2
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
0.75
0.029
S
8 (max.)
P013I
SO16L MECHANICAL DATA
ST21S07A
7/10
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
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
0
o
4
o
8
o
0
o
4
o
8
o
L
0.50
0.60
0.70
0.020
0.024
0.028
c
E
b
A2
A
E1
D
1
PIN 1 IDENTIFICATION
A1
L
K
e
TSSOP20 MECHANICAL DATA
ST21S07A
8/10
ST21S07A
9/10
ST21S07A
10/10
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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.
The ST logo is a registered trademark of STMicroelectronics
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