Datasheet ST21S07ACWR, ST21S07ACW, ST21S07ACTR Datasheet (SGS Thomson Microelectronics)

1/10February 2001

■ FULLY COMPLIANT WITH SCSI , SC SI-2

AND EMERGING SCSI-E STANDARDS

■ PROVIDES ACTIVE TERMINATION FOR

NINE SIGNAL LINES

■ LOW DROPOUT (0.5V) VREGS:2.85V

■ FACTORY TRIMMED TERMINATI ON 110Ω

(±2%)

■ POWER DOWN MODE ISOLATES

TERMINATION RESISTORS FROM THE
BUS

■ FULLY SUPPORTS ACTI VELY 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

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 110Ω termination resistors into a
monolithic IC. The ST21S07A can be electri cally
isolatesd from the SCSI bus without physical
removal from the SCSI device.

ORDERING CODES

(*) Avai l abl e on reque st

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 Termina tion Power 1: Should be connected to the SCSI TERMPWR line.

Must be decoupled with either a 2.2µF or 4.7µF. 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.
32R1Signal Termination 1: 110 Ω Termination
43R2Signal Termination 2: 110 Ω Termination
54R3Signal Termination 3: 110 Ω Termination
65R4Signal Termination 4: 110 Ω Termination
76R5Signal Termination 5: 110 Ω Termination
8 HS-GND Heat Sink Ground: Internally connected to the mounting pad. Should be

either grounded or electrically isolated from the other circuitry.
97V

REF1

Reference Voltage 1: Must be external connected directly to the V

REF2

pin. Must be decoupoled with 4.7µF 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 2.2µF or 4.7µF. 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 Ω Termination
14 11 R7 Signal Termination 7: 110 Ω Termination
15 12 R8 Signal Termination 8: 110 Ω Termination
16 13 R9 Signal Termination 9: 110 Ω 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 4.7µF 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 70°C, unless otherwise specified.)

REGULATOR CHARACTERISTICS (T

A

= 0 to 70°C, unless otherwise specified.)

Note 1: TERMPWR = 4V to 5.5V
Note2: Si gnal Lines = 0V to T ER M PWR
Note3: Al l signal lines = 0V
Note 4: Al l s i gnal lines open
Note 5: PD

= 0V
Note 6: Gua ranteed by design; not production t ested
Note 7: R

1

through R9 only

Note 8: R

1

through R9 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 VTP+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 µA

R

TERM

Termination Resistance (note 1, 2) 108 110 112 Ω

T

SD

Die Thermal Shutdown (note 1, 6) 150 170 °C

C

PD

Power Down Termniatio N
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 µA

I

IL

Input Leackage Low (note 1, 7) 1 µA

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 bu ffer prod uc e 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 ST21S 07A from the signal l ines 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 connecte d 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 SCS I 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 e ach 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

= 4.7µF tantalium C2 = 2.2µF tantali um or 4.7mF alumi num

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 derive d
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 by pass capaci tor (0.1µF recommended) can be added in parallel to C1 for applications using fast rise/f al l tim e drivers.

ST21S07A

6/10

DIM.

mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A2.650.104
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

C0.5 0.020
c1 45 (typ.)

D 10.1 10.5 0.397 0.413

E 10.0 10.65 0.3.93 0.419

e1.27 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

M0.750.029

S8 (max.)

P013I

SO16L MECHANICAL DATA

ST21S07A

7/10

DIM.

mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A1.10.433

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

K0

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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