4

408-432-9100/www.impweb.com

© 2000 IMP, Inc.

Application Information

IMP5115 Maximizes Line Current

Cable transmission theory suggests to optimize signal speed and

quality, the termination should act both as an ideal voltage refer-

ence 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 resis-

tors (typically 110

Ω) are a compromise. With coventional linear

terminators as the line voltage increases the amount of current

decreases linearly by the equation;

The IMP5115, with its unique new architecture, applies the maxi-

mum amount of current regardless of line voltage until the

termination high threshold (2.85V) is reached.

Acting as a near ideal line terminator, the IMP5115 closely repro-

duces the optimum case when the device is enabled. To enable the

device the Disable pin must be driven LOW. When enabled,

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

demands by delivering 24mA on assertion and by imposing 2.85V

on de-assertion.

Disable/Sleep Mode

Disable mode places the device in a sleep state, where quiescent

current typically 375

µA. When disabled, all outputs are in a high

impedance state. Sleep mode can be used for power conservation

or to remove the terminator from the SCSI chain.

An additional feature of the IMP5115 are their compatibility with

active negation drivers.

VV

R

I

REF

LINE

−

()

= .

Figure 3.

5115_03.eps

1 Meter, AWG 28

IMP5115

Receiver

Driver

IMP5115

Figure 1. Receiving Waveform – 20MHz

Figure 2. Driving Waveform – 20MHz

e

l

b

a

s

i

Ds

t

u

p

t

u

Ot

n

e

r

r

u

C

t

n

e

c

s

e

i

u

Q

Hd

e

l

b

a

n

EA

m

6

Le

c

n

a

d

e

p

m

I

h

g

i

H

/

d

e

l

b

a

s

i

D5

7

3

µA

n

e

p

Od

e

l

b

a

n

EA

m

6

s

p

e

.

4

0

t

_

5

1

1

5

Table 1. Power Up/ Power Down Function Table

1

IMP5