ML6509CS Micro Linear, ML6509CS Datasheet

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ML6509CS

Manufacturer Part Number
ML6509CS
Description
Active SCSI terminator
Manufacturer
Micro Linear
Datasheet

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GENERAL DESCRIPTION
The ML6509 BiCMOS SCSI terminator provides active
termination in a SCSI system with single ended drivers and
receivers, in full compliance with the SCSI-1, SCSI-2 and
SCSI-3 recommendations. It provides a 2.85V reference
through an internal 1V dropout linear regulator. Active
SCSI termination helps the system designer to effectively
control analog transmission line effects like ringing, noise,
crosstalk, ground bounce, etc. In addition it provides
greater immunity to voltage drops on the TERMPWR line
of the SCSI bus. The desired V-I characteristics for signal
negation requires that the terminator source 0–24mA
while maintaining 2.85V and for signal assertion
preferably follow a linear slope of 110 . The ML6509
attempts to provide a V-I characteristic optimized to
minimize the transmission line effects during both signal
assertion and negation, using a MOSFET based
architecture. The desired V-I characteristic is achieved by
trimming one resistor in the control block. It provides
negative clamping for signal assertion transients and
current sink capability, to handle active negation driver
overshoots above 2.85V, which is currently accomplished
with external components in SCSI subsystems today. It
provides a disconnect mode, where the terminator is
completely disconnected from the SCSI
bus and the output capacitance is < 5pF, typically.
BLOCK DIAGRAM
NCLAMP = Negative Clamp
GND
NCLAMP
NCLAMP
NCLAMP
1V DROPOUT
REGULATOR
TERMPWR
LINEAR
MOSFETs WITH I
9 TERMINATION LINES
NORMAL MODE
. . .
2.85V
. . .
MAX
= 24mA
216mA
(MAX)
FEATURES
* Some Packages Are End Of Life As Of August 1, 2000
V
REF
Fully monolithic IC solution providing active
termination for 9 lines of the SCSI bus
Low dropout voltage (1V) linear regulator, trimmed for
accurate termination current, with 300mA current
source capability
Output capacitance typically <5pF
Disconnect mode — logic pin to disconnect terminator
from the SCSI bus, <100µA
Lowpower mode — for power conscious, portable
system & peripheral applications, using less than 6"
cables. (Equivalent to a 1mA current drive with a
2.5k
Current sinking — can sink current >10mA per line to
handle active negation driver overshoots above 2.85V
Negative clamping on all lines to handle signal
assertion transients
Regulator can source 200mA and sink 50mA while
maintaining regulation
Current limit & thermal shutdown protection
Small and low profile package options; 16-pin SOIC
(300 mil), 20-pin TSSOP (1 mil height)
Active SCSI Terminator
termination)
MOSFETs WITH I
LOW POWER MODE
R
TRIM
DISCNKT
2.85V
V
MAX
REF
. . .
= 1mA
LPWR
CONTROL
BLOCK
ML6509*
February 1997
1

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ML6509CS Summary of contents

Page 1

GENERAL DESCRIPTION The ML6509 BiCMOS SCSI terminator provides active termination in a SCSI system with single ended drivers and receivers, in full compliance with the SCSI-1, SCSI-2 and SCSI-3 recommendations. It provides a 2.85V reference through an internal 1V dropout ...

Page 2

ML6509 GENERAL DESCRIPTION One unique feature of the ML6509 is its support for a Low Power mode, for use in Notebook and portable computer applications, where it provides a 1mA (approximately 2.5K termination) for less than 6" cable lengths. This ...

Page 3

ABSOLUTE MAXIMUM RATINGS Signal Line Voltage ............................. –0.3 to TERMPWR +0.3V Regulator Output Current ................................... –100 to 300mA TERMPWR Voltage ..................................................... –0 Storage Temperature .......................................... –65°C to 150°C Soldering Temperature ..................................... 260°C for 10 sec Thermal Impedance ( ...

Page 4

ML6509 FUNCTIONAL DESCRIPTION The SCSI terminator helps in decreasing the transmission line effects with precise termination. Termination is conventionally provided at the beginning and end of the SCSI bus, however when additional peripherals are added, the termination needs to be ...

Page 5

Thus in an 8-bit wide SCSI bus arrangement (“A” cable), two ML6509s would be needed at each end of the SCSI cable in order to terminate the 18 active signal lines. 16-bit wide SCSI would use three ML6509s, while 32-bit ...

Page 6

ML6509 This is a very important characteristic that the terminator helps overcome by increasing the noise margin and boosting the step as high as possible. This capability for the ML6509 implementation is illustrated in the attached simulation graphs which show ...

Page 7

ML6509 SCSI TERMINATOR DRIVER END 2V 0.8V TERMINATOR END 2V 0.8V 100ns TIME (SECONDS) BOULAY TERMINATOR DRIVER END 2V 0.8V TERMINATOR END 2V 0.8V 100ns TIME (SECONDS) Conditions Low Cable impedance of 110 (worst case 10ns D 10 ...

Page 8

ML6509 DRIVER END 2V 0.8V TERMINATOR END 2V 0.8V DRIVER END 2V 0.8V TERMINATOR END 2V 0.8V Conditions Figure 6a. Signal Assertion/Negation Waveforms (Simulated) 8 ML6509 SCSI TERMINATOR 100ns 200ns TIME (SECONDS) BOULAY TERMINATOR 100ns 200ns TIME (SECONDS) Low Cable ...

Page 9

PHYSICAL DIMENSIONS 0.251 - 0.262 (6.38 - 6.65) 20 PIN 0.026 BSC (0.65 BSC) 0.008 - 0.012 0.033 - 0.037 (0.20 - 0.30) (0.84 - 0.94) inches (millimeters) Package: T20 20-Pin TSSOP 0.169 - 0.177 0.246 - ...

Page 10

... ORDERING INFORMATION PART NUMBER ML6509CS ML6509CT (EOL) © Micro Linear 1997 is a registered trademark of Micro Linear Corporation Products described herein may be covered by one or more of the following patents: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,594,376. Other patents are pending. ...

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