DS21T05Z+ datasheet, PDF - EEWORLD Datasheet

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DS21T05Z+: Description9-LINE 110 ohm SCSI BUS TERMINATOR, PDSO16, 0.150 INCH, PLASTIC, SOIC-16; CategoryAnalog mixed-signal IC Drivers and interfaces; File Size781KB，8 Pages; ManufacturerRochester Electronics; Websitehttps://www.rocelec.com/; Environmental Compliance

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DS21T05Z+ Overview

9-LINE 110 ohm SCSI BUS TERMINATOR, PDSO16, 0.150 INCH, PLASTIC, SOIC-16

DS21T05Z+ Parametric

Parameter Name	Attribute value
Is it lead-free?	Lead free
Is it Rohs certified?	conform to
Maker	Rochester Electronics
Parts packaging code	SOIC
package instruction	SOP,
Contacts	16
Reach Compliance Code	unknown
Differential output	NO
Interface integrated circuit type	SCSI BUS TERMINATOR
JESD-30 code	R-PDSO-G16
JESD-609 code	e3
length	9.9 mm
Humidity sensitivity level	1
Number of functions	1
Number of signal lines	9
Number of terminals	16
Maximum operating temperature	70 °C
Minimum operating temperature
Package body material	PLASTIC/EPOXY
encapsulated code	SOP
Package shape	RECTANGULAR
Package form	SMALL OUTLINE
Peak Reflow Temperature (Celsius)	260
Nominal pull-up resistor	110 Ω
Certification status	COMMERCIAL
Maximum seat height	1.75 mm
Maximum supply voltage	5.5 V
Minimum supply voltage	4 V
Nominal supply voltage	5 V
surface mount	YES
Temperature level	COMMERCIAL
Terminal surface	MATTE TIN
Terminal form	GULL WING
Terminal pitch	1.27 mm
Terminal location	DUAL
Maximum time at peak reflow temperature	NOT SPECIFIED
width	3.9 mm

DS21T05Z+ Preview

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DS21T05

SCSI Terminator

www.dalsemi.com

FEATURES

PIN ASSIGNMENT

Fully compliant with SCSI-1, Fast SCSI and

Ultra SCSI

TERMPWR1

Functionally compatible to the DS21T07,

VREF2

targeted for high volume applications

Provides active termination for nine signal

lines

Laser-trimmed 110-ohm termination resistors

VREF1

have 5% tolerance

GND

TERMPWR2

Low dropout voltage

DS21T05Z 16-Pin SOIC (150-mil)

Power-down mode isolates termination

resistors from the bus

TERMPWR1

SCSI bus hot-plug compatible

VREF2

Fully supports actively negated SCSI signals

Onboard thermal shutdown circuitry

16-pin plastic narrow SOIC

VREF1

GND

TERMPWR2

DS21T05S 16-Pin SOIC (300-mil)

DESCRIPTION

Fast SCSI and Ultra SCSI require the use of active terminations at both ends of every cable segment in a

SCSI system with single-ended drivers and receivers. The DS21T05 SCSI Terminator, which is fully

compliant with these standards, enables the designer to gain the benefits of active termination: greater

immunity to voltage drops on the TERMPWR (TERMination PoWeR) line, enhanced high-level noise

immunity, intrinsic TERMPWR decoupling, and very low quiescent current consumption. The DS21T05,

which integrates a regulator and nine precise-switched, 110-ohm termination resistors into a monolithic

IC, is a functionally compatible version of the DS21T07. With relaxed output current and termination

tolerances, the DS21T05 is intended for high volume applications which require active termination but

not the high performance of the DS21T07.

FUNCTIONAL DESCRIPTION

The DS21T05 consists of a bandgap reference, buffer amplifier, and nine termination resistors (Figure 1).

The bandgap reference circuit produces a precise 2.55V level which is fed to a buffer amplifier. The

buffer produces a 2.85V level and is capable of sourcing at least 24 mA 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,

1 of 7

112099

DS21T05

the buffer can sink 200 mA, and V

REF

will move less than 60 mV. When all lines settle in the quiescent

state, the regulator will consume about 5 mA. When the DS21T05 is put into power-down mode by

bringing

low, the power-down circuitry will turn off the transistors on each signal line. This will

isolate the DS21T05 from the signal lines and effectively remove it from the circuit. The power-down pin

(

) has an internal 50 kΩ=pullup resistor. To place the DS21T05 into an active state, the

pin should

be left open circuited. When installed on disk drives or RAID system components, the DS21T05 will not

affect the SCSI bus during a hot plug operation.

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

DS21T05 requires a 4.7

µF

capacitor connected between the VREF pins and ground. Figure 2 details a

typical SCSI bus configuration. In an 8-bit wide SCSI bus arrangement, two DS21T05s would be needed

at each end of the SCSI cable in order to terminate the 18 active signal lines. In a 16-bit wide SCSI bus

arrangement, three DS21T05’s would be needed at each end of the SCSI cable in order to terminate the

27 active signal lines.

DS21T05 BLOCK DIAGRAM

Figure 1

2 of 7

DS21T05

TYPICAL SCSI BUS CONFIGURATION

Figure 2

DS21T05

NOTES:

1. C1 = 4.7

µF

tantalum

C2 = 2.2

µF

tantalum or 4.7

µF

aluminum

2. If the DS21T05 is to be embedded into a peripheral that will act as a target on a SCSI bus, it is

recommended that 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

µF

recommended) can be added in parallel to C1 for

applications using fast rise/fall time drivers.

3 of 7

DS21T05

PIN DESCRIPTION

Table 1

DS21T05Z

SYMBOL

TERMPWR1

VREF1

DESCRIPTION

Termination Power 1.

Should be connected to the SCSI TERMPWR

line. Must be decoupled with either a 2.2 µF or 4.7 µF. See Figure 2.

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. Must be decoupled with a 4.7 µF capacitor as shown in

Figure 2.

Ground.

Signal ground; 0.0V.

Termination Power 2.

Should be connected to the SCSI TERMPWR

line. Must be decoupled with either a 2.2 µF or 4.7 µF. See Figure 2.

No Connect.

Do not connect any signal to this pin.

Signal Termination 6.

110-ohm termination.

Signal Termination 7.

110-ohm termination.

Signal Termination 8.

110-ohm termination.

Signal Termination 9.

110-ohm termination.

Reference Voltage 2.

Must be externally connected directly to the

VREF1 pin. Must be decoupled with a 4.7 µF capacitor as shown in

Figure 2.

Power Down.

When tied low, the DS21T05 enters a power-down

mode. Contains an internal 50K pull-up. Strap low to deactivate the

DS21T05, leave open circuited to activate the DS21T05.

GND

TERMPWR2

VREF2

4 of 7

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