IMP5241/42/431
Pin Description
Pin Name
Function
1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9-
Negative signal termination lines for LVD mode. Signal termination lines for SE mode.
1+, 2+, 3+, 4+, 5+, 6+, 7+, 8+, 9+ Positive signal termination lines for LVD mode. Pseudo-ground lines for SE mode.
VTERM
Power supply pin for terminator. Connect to SCSI bus TermPwr. Must be decoupled by one
4.7µF low-ESR capacitor for every three terminator devices. It is absolutely necessary to
connect this pin to the decoupling capacitor through a very low impedance (big traces on PCB).
Keeping distances very short from the decoupling capacitors to the VTERM pin is also critical.
The value of the decoupling capacitor is somewhat layout dependant and some applications
may benefit from an additional 0.1µF decoupling capacitor at the VTERM pin.
DISCONNECT (IMP5241)
DISCONNECT (IMP5242)
Enables / disables terminator. See Table 2 for logic levels.
GND
Terminator ground pin. Connect to ground.
MASTER / SLAVE
Sometimes referred to as M/S pin. Used to select which terminator is the controlling device.
MASTER/SLAVE pin HIGH or Open enables the DIFFSENSE output drive. See Table 1.
DIFFSENSE
DIFF B
This is a dual function pin. It drives the SCSI bus DIFFSENS line. It is also the sense pin to
detect the SCSI bus mode (LVD, SE or HVD). DIFFSENSE output drive can be disabled with a
LOW level on the MASTER/SLAVE pin. See Table 1 and Table 2. Internally connected to DIFF
B pin through 20kΩ resistor.
Internally connected to DIFFSENSE pin through 20kΩ resistor. It can be used as a mode sense
pin when the device is a non-controlling terminator (MASTER/SLAVE pin is LOW). An RC filter
(20kΩ / 0.1µF) is not required on the IMP5241/42, as it has an internal timer.
SE
LVD
Single-ended output. When HIGH, the terminator is operating in SE mode.
Low Voltage Differential output. When HIGH, the terminator is operating in LVD mode.
High Voltage Differential output. When HIGH, the terminator is operating in HVD mode.
HVD
HEATSINK
Attached to die mounting pad, but not bonded to GND pin. Pins should be considered a heat
sink only, and not a true ground connection. It is recommeneded that these pins be connected to
ground, but can be left floating.
5241/42_t08.at3
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3
© 2001 IMP, Inc.
Data Communications
A1PROS [ A1 PROS CO., LTD. ]
