LX5111/5112

PRODUCT DA T ABOOK 1996/1997

Copyright © 1997

Rev. 1.1

12/97

4

UltraMAX

BLOCK DIAGRAM

FUNCTIONAL DESCRIPTION

THERMAL

LIMITING

CIRCUIT

TERM POWER

CURRENT

BIASING

CIRCUIT

1.4V

DISCONNECT (5111)

DISCONNECT (5112)

24mA CURRENT

LIMITING CIRCUIT

DATA OUTPUT

PIN DB(0)

2.85V

1 OF 9 CHANNELS

Cable transmission theory suggests to optimize signal speed

and quality, the termination should act both as an ideal voltage

reference when the line is released (deasserted) and as an ideal

current source when the line is active (asserted).

Common

active terminators, which consist of Linear Regulators in series

with resistors (typically 110

Ω), are

a compromise. As the line voltage

increases, the amount of current

decreases linearly by the equation

V = I * R. The LX5111/5112, with

their unique new architecture ap-

plies the maximum amount of

current regardless of line voltage

until the termination high threshold

(2.85V) is reached.

Acting as a near ideal line terminators, the LX5111/5112

closely reproduce the optimum case when the devices are

enabled.

To enable the device the DISCONNECT pin

(DISCONNECT pin for the LX5112) must be pulled logic High

(logic Low for the LX5112). During this mode of operation,

quiescent current is 6mA and the devices will respond to line

demands by delivering 24mA on assertion, and by imposing

2.85V on deassertion.

In order to disable the device, the

DISCONNECT pin (DISCONNECT pin for the LX5112) must be

driven logic Low (logic High for the LX5112). This mode of

operation places the devices in a sleep state where a meager

275µA of quiescent current is consumed. Additionally, all outputs

are in a Hi-Z (impedance) state.

Sleep mode can be used for power

conservation or to completely elimi-

nate the terminator from the SCSI

chain. In the second case, termi-

nation node capacitance is impor-

tant to consider.

The terminators

will appear as a parasitic distributed

capacitance on the line, which can

detract from bus performance. For

this reason, the LX5111/5112 have been optimized to have only

3pF of capacitance per output in the sleep state.

An additional feature of the LX5111/5112 IC's are their

compatibility with active negation drivers. These devices handle

up to 60mA of sink current for drivers which exceed the 2.85V

output high.

UltraMAX is a trademark of Linfinity Microelectronics Inc.

Outputs

Quiescent

Current

H

L

Enabled

6mA

L

H

HI Z

275µA

Open

Open

HI Z

275µA

LX5111

LX5112

DISCONNECT

DISCONNECT

PRODUCTION DATA - Information contained in this document is proprietary to Linfinity, and is current as of publication date. This document

may not be modified in any way without the express written consent of Linfinity. Product processing does not necessarily include testing of

all parameters. Linfinity reserves the right to change the configuration and performance of the product and to discontinue product at any time.