DS2119ME/T&R - Maxim Integrated - Datasheet.Directory

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FEATURES

 Fully Compliant with SCSI SPI-2, SPI-3,

SPI-4, Ultra160, and Ultra320

 Provides Multimode Low-Voltage

Differential/Single-Ended (LVD/SE)

Termination for Nine Signal Line Pairs

 Autoselection of LVD or SE Termination

 5% Tolerance on SE and LVD Termination

Resistance

 Low Power-Down Capacitance of 3pF

 On-Board Thermal Shutdown Circuitry

 SCSI Bus Hot Plug Compatible

 Fully Supports Actively Negated SE SCSI

Signals

PIN CONFIGURATION

ORDERING INFORMATION

PART VOLTAGE

(V) TEMP RANGE PIN-PACKAGE TOP MARK*

DS2119ME 5

0°C to +70°C 28 TSSOP (0.173") DS2119M

DS2119ME+ 5

0°C to +70°C 28 TSSOP (0.173") DS2119M

DS2119ME/T&R 5 0°C to +70°C 28 TSSOP (0.173")/Tape

and Reel DS2119M

DS2119ME+T&R 5 0°C to +70°C 28 TSSOP (0.173")/Tape

and Reel DS2119M

+ Denotes a lead-free/RoHS-compliant package.

* The top mark includes a "+" on lead-free packages.

DETAILED DESCRIPTION

The DS2119M Ultra3 LVD/SE SCSI terminator is both a low-voltage differential (LVD) and single-

ended (SE) terminator. The multimode operation enables the designer to implement LVD in current

products while allowing the end-user SE-backward compatibility with legacy devices. If the device is

connected in an LVD-only bus, the DS2119M will use LVD termination. If any SE devices are connected

to the bus, the DS2119M will use SE termination. This is accomplished automatically inside the part by

sensing the voltage on the SCSI bus DIFFSENS line.

For the LVD termination, the DS2119M integrates two current sources with nine precision resistor

strings. For the SE termination, one regulator and nine precision 110Ω resistors are used. Three

DS2119M terminators are needed for a wide SCSI bus.

DS2119M

Ultra3 LVD/SE SCSI Terminato

www.maxim-ic.com

R9N

R9P

R8N

HS GND

R7N

R7P

R6N

R6P

DIFF_CAP

DIFFSENSE

MSTR/SLV

R8P

RIN

R2P

R2N

R3P

R4P

R4N

R5P

R5N

ISO

GND

HS GND

TSSOP

VREF

RIP

TPWR

R3N

DS2119M

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REFERENCE DOCUMENTS

Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface (SPI) Project: 0855-M, 1995

Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface 2 (SPI-2) Project: 1142-M, 1998

Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface 3 (SPI-3) Project: 1302-D, 1999

Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface 4 (SPI-4) Project: 1365-D, 200x

Available From:

American National Standards Institute (ANSI) Phone: (212) 642-4900

Global Engineering Documents 15 Inverness Way East; Englewood, CO 80112 Phone: (800) 854-7179

FUNCTIONAL DESCRIPTION

The DS2119 combines LVD and SE termination with DIFFSENS sourcing and detection.

A bandgap reference is fed into two amplifiers, which creates a 1.25V reference voltage and a 2.85V

reference voltage. The control logic determines which of these references will be applied to the

termination resistors. If the SCSI bus is in LVD mode, then the 1.25V reference will be used. If the SCSI

bus is in SE mode, then the 2.85V reference will be used. That same control logic will switch in/out

parallel resistors to change the total termination resistance accordingly. Finally, in SE mode, the Rp pins

will be switched to ground.

The DIFFSENSE circuitry decodes trinary logic. There will be one of three voltages on the SCSI control

line called DIFFSENS. Two comparators and a NAND gate determine if the voltage is below 0.6V, above

2.15V, or in between. That indicates the mode of the bus to be SE, HVD, or LVD, respectively.

The DS2119M’s DIFF_CAP pin monitors the DIFFSENS line to determine the proper operating mode of

the device. The DIFFSENSE pin can also drive the SCSI DIFFSENS line (when MSTR/SLV = 1) to

determine the SCSI bus-operating mode. The DS2119M switches to the termination mode that is

appropriate for the bus based on the value of the DIFFSENS voltage. These modes are:

 LVD Mode: LVD termination is provided by a precision laser-trimmed resistor string with two

current sources. This configuration yields a 105Ω differential and 150Ω common-mode

impedance. A fail-safe bias of 112mV is maintained when no drivers are connected to the SCSI

bus.

 SE Mode: When the external driver for a given signal line turns off, the active terminator will pull

that signal line to 2.85V (quiescent state). When used with an active negation driver, the power

amp can sink 22mA per line and the reference voltage will move less than 100mV. The

terminating resistors maintain their 110Ω value.

 HVD Isolation Mode: The DS2119M identifies that there is an HVD (high-voltage differential)

device on the SCSI bus and isolates the termination pins from the bus.

When ISO = 1, the termination pins are isolated from the SCSI bus, VREF remains active. During thermal

shutdown, the termination pins are isolated from the SCSI bus and VREF becomes high impedance. The

DIFFSENSE driver is shut down during either of these two events.

To ensure proper operation, the TPWR pin should be connected to the SCSI bus TERMPWR line. As

with all analog circuitry, the TERMPWR and VDD lines should be bypassed locally. A 2.2µF capacitor

and a 0.01µF high-frequency capacitor are recommended between TPWR and ground and placed as close

DS2119M

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as possible to the DS2119M. The DS2119M should be placed as close as possible to the SCSI connector

to minimize signal and power-trace length, thereby resulting in less input capacitance and reflections,

which can degrade the bus signals.

To maintain the specified regulation, a 4.7µF capacitor is required between the VREF pin (VREF) and

ground of each DS2119M. A high frequency cap (0.1µF ceramic recommended) can also be placed on the

VREF pin in applications that use fast rise/fall time drivers. A typical SCSI bus configuration is shown in

Figure 2.

 DIFFSENS Noise Filtering: The DS2119M incorporates a digital filter to remove high-frequency

transients on the DIFFSENS control line, thereby eliminating erroneous switching between

modes. This filter eliminates the need for the external capacitor and resistor, which heretofore

performed this function.

NOTES:

1) DIFFSENS. Refers to the SCSI bus signal.

2) DIFFSENSE. Refers to the Dallas Semiconductor pin name and internal circuitry relating the

DIFFSENS driver.

DS2119M

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Figure 1. DS2119M Block Diagram

DS2119M

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Figure 2. SCSI Bus Configuration

DS2119M

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PIN DESCRIPTION

PIN NAME FUNCTION

1 VREF

Reference Voltage. 2.85V reference in SE mode and 1.25V reference in

LVD mode; must be decoupled with a 4.7µF cap.

2–5, 7–12,

18–21, 23–26

RxP,

RxN Signal Termination. Connect to SCSI bus signal lines.

6, 22 HS GND Heat Sink Ground. Internally connected to the mounting pad. Should

be grounded.

13 ISO

Isolation. When pulled high, the DS2119M isolates its bus pins (RxP,

RxN) from the SCSI bus.

14 GND Ground. Signal ground; 0V.

15 MSTR/SLV

Master/Slave. Mode-select for the noncontrolling terminator. When

pulled high, MSTR enables the DIFFSENSE driver.

16 DIFFSENSE DIFFSENSE. Output to drive the SCSI bus DIFFSENS line.

17 DIFF_CAP

DIFFSENSE Capacitor. Connect a 0.1µF capacitor for DIFFSENSE

filter. Input to detect the type of device (differential or single-ended) on

the SCSI bus.

27, 28 TPWR Termination Power. Connect to the SCSI TERMPWR line and

decouple with a 2.2µF capacitor.

RECOMMENDED OPERATING CONDITIONS

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

SE Mode VTPWR(SE) 4.0 5.5 V

Termpower

Voltage LVD Mode VTPWR(LVD) 2.7 5.5 V

Logic 0 VIL -0.3 +0.8 V

Logic 1 VIH 2.0

VTPWR +

0.3 V

Operating Temperature VAMB 0 70 °C

DS2119M

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SINGLE-ENDED CHARACTERISTICS

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

SE Termination

Resistance

RSE 104.5 110 115.5 Ω 1

SE Voltage Reference VREF 2.7 2.85 3.0 V

SE Output Current lOSE 25.4 mA 2

Output Capacitance COUT 3 pF 3

LOW-VOLTAGE DIFFERENTIAL CHARACTERISTICS

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Differential Mode

Termination Resistance RDM 100 110 Ω

Common Mode

Termination Resistance RCM 110 190 Ω

Differential Mode Bias VDM 100 125 mV 4

Common Mode Bias VCM 1.125 1.375 V

DC CHARACTERISTICS

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Termpower Current ITPMR 12 mA 4

Input Leakage High IIH -1.0 µA

Input Leakage Low IIL 1.0 µA

Output Current High IOH -1.0 mA 5, 7

Output Current Low IOL 4.0 mA 6, 7

DIFFSENS SE

Operating Range VSEOR -0.3 0.5 V

DIFFSENS LVD

Operating Range VLVDOR 0.7 1.9 V

DIFFSENS HVD

Operating Range VHVDOR 2.4 VTPWR +

0.3 V

DIFFSENSE Driver

Output Voltage VDSO 1.2 1.4 V 8, 9

DIFFSENSE Driver

Source Current IDSH 5 15 mA 8, 10, 12

DIFFSENSE Driver

Sink Current IDSL 20 200 µA 8, 11

Thermal Shutdown 150 ºC 3

DS2119M

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REGULATOR CHARACTERISTICS

(TA = 0°C to +70°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Line Regulation LIREG 1.0 2.5 %

Load Regulation LOREG 1.3 3.5 %

Current Limit ILIM 550 mA

Sink Current ISINK 200 mA

NOTES:

1) VLINE = 0V to 3V.

2) VLINE = 0.2V.

3) Guaranteed by design.

4) All lines open.

5) VOUT = 2.4V.

6) VOUT = 0.4V.

7) SE/LVD/HVD pins only.

8) MSTR/SLV = 1.

9) IDS = 0mA to 5mA.

10) VDSO = 0V.

11) VDSO = 2.75V.

12) TPWR = 5.5V.

DS2119M

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Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product.

No circuit patent licenses are implied. Maxim/Dallas Semiconductor reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor Corporation.

PACKAGE INFORMATION

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package

outline information, go to www.maxim-ic.com/DallasPackInfo.)