Datasheet

SCBA015A
7–34
Fast GTLP Backplanes With the GTLPH1655
Input Output
ERC = GND
5 ns 10 ns 15 ns 20 ns 25 ns 30 ns0 ns
4.00 V
3.00 V
2.00 V
1.00 V
0.00 V
–1.00 V
–2.00 V
Figure 26. Rising Edge, ERC = GND (Fast Edges), Input Signals t
r
= 2 ns, 10 ns
Removal and Insertion Under Voltage and Partially Switched-Off Systems
If it is possible to remove and reinsert plug-in boards in a system while it remains in operation
(live insertion), special precautions must be taken with the signal lines.
• The outputs of the boards to be inserted or removed must be at a high impedance when the
boards are inserted or removed.
• Before inserting a board, all pins must be charged to the threshold voltage (1.5 V with
TTL-compatible systems, or V
CC
/2 with CMOS-compatible systems). Thus, destructive
voltage spikes on the signal line in excess of the threshold voltage range, which might
otherwise corrupt the data on the bus, can be avoided.
Figure 27 shows this principle. The data pins are charged to the switching threshold (V
TH
). As a
maximum, the switching threshold can be reached when inserting; however, it no longer can be
exceeded as a result of a voltage spike.