IMP5111/5112
IMP5218
Application Information
Figure 1. Receiving Waveform – 20MHz
Figure 2. Driving Waveform – 20MHz
Receiver
Driver
1 Meter, AWG 28
IMP5218
IMP5218
5218_03.eps
Figure 3.
device the Disconnect 1 and Disconnect 2 pins must be driven per
Table 1. 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.
IMP5218 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 110Ω) are a compromise. With coventional linear
terminators as the line voltage increases the amount of current
decreases linearly by the equation;
Disable/ Sleep Mode
Disable/ Sleep mode can be used for power conservation or to
remove the terminator from the SCSI chain.
The IMP5218 is disabled when both disconnect pins are driven
logic LOW.
V
REF − V
(
)
= I.
LINE
R
Disable mode places the device in a sleep state, where quiescent
current is typically 375µA. When disabled, all outputs are in a
high impedance state and each output has only 3pF of capaci-
tance.
The IMP5218, 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.
An additional feature of the IMP5218 is its compatibility with
active negation drivers.
Acting as a near ideal line terminator, the IMP5218 closely repro-
duces the optimum case when the device is enabled. To enable the
4
408-432-9100/ www.impweb.com
© 2000 IMP, Inc.
A1PROS [ A1 PROS CO., LTD. ]
