LX5111A/5112A

PRODUCT DA T ABOOK 1996/1997

Copyright © 1999

Rev. 0.1

3/99

4

UltraMAX

BLOCK DIAGRAM

FUNCTIONAL DESCRIPTION

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 LX5111A/5112A, 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 LX5111A/5112A

closely reproduce the optimum case when the devices are

enabled.

To enable the device the DISCONNECT pin

(DISCONNECT pin for the LX5112A) must be pulled logic High

(logic Low for the LX5112A). 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 LX5112A) must

be driven logic Low (logic High for the LX5112A). This mode

of operation places the devices in a sleep state where a meager

275µA of quiescent current is con-

sumed. Additionally, all outputs are

in a Hi-Z (impedance) state. Sleep

mode can be used for power con-

servation or to completely eliminate

the terminator from the SCSI chain.

In the second case, termination

node capacitance is important to

consider. The terminators will ap-

pear as a parasitic distributed capaci-

tance on the line, which can detract from bus performance. For

this reason, the LX5111A/5112A have been optimized to have

only 3pF of capacitance per output in the sleep state.

An additional feature of the LX5111A/5112A IC's are their

compatibility with active negation drivers.

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

LX5111A

LX5112A

DISCONNECT

DISCONNECT

PRELIMINARY DATA - Information contained in this document is pre-production data, and is proprietary to LinFinity. It may

not modified in any way without the express written consent of LinFinity. Product referred to herein is offered in sample form

only, and Linfinity reserves the right to change or discontinue this proposed product at any time.