IMP5111/5112
Application Information
Figure 1. Receiving Waveform – 20MHz
Figure 2. Driving Waveform – 20MHz
Receiver
Driver
1 Meter, AWG 28
IMP5111
IMP5112
IMP5111
IMP5112
5111/5112_03.eps
Figure 3.
IMP5111/ IMP5112 Maximizes Line Current
Disable / Sleep Mode
Cable transmission theory suggests to optimize signal speed and The IMP5111 has an active LOW disconnect pin, and the IMP5112
quality, the termination should act both as an ideal voltage refer- has an active HIGH disconnect pin. The disable mode is entered
ence when the line is released (deasserted) and as an ideal if the disconnect pin on either device is left open.
current source when the line is active (asserted). Common active
When disabled the termination lines are in a high impedance
terminators which consist of linear regulators in series with resis-
state, and the power supply current drops to 275µA typically. The
tors (typically 110Ω) are a compromise. With coventional linear
disable mode can be used to save power or completely eliminate
terminators as the line voltage increases the amount of current
the terminator from the SCSI bus.
decreases linearly by the equation;
Disabled terminators appear as distributed capacitance on the
bus. The IMP5111/ 5112 have been optimized to have only 3pF of
capacitance per output when in the disabled mode.
V
REF − V
(
)
= I.
LINE
R
The IMP5111/ 5112, with their unique architecture, applies the
maximum amount of current regardless of line voltage until the
termination high threshold (2.85V) is reached.
The IMP5111/ 5112 are compatible with active negation drivers.
The devices will handle up to 60mA of sink current for drivers
which exceed the 2.85V output high level
.
Table 1. Power Up/ Power Down Function Table
IMP5111
DISCONNECT
IMP5112
DISCONNECT
Outputs
Quiescent Current
H
L
Enabled
6mA
L
H
Disabled/High Impedance
Disabled/High Impedance
275µA
275µA
Open
Open
5111/5112_t04a.eps
4
www.ds-imp.com.cn
Daily Silver IMP
IMP [ IMP, INC ]
