Datasheet
SCEA019 - January 2001
7–104 Texas Instruments GTLP Frequently Asked Questions
21 What is important about live insertion?
Many backplane systems in communications applications must remain operational 24 hours a
day, 7 days a week. These systems cannot be shut down when a board is inserted or
removed from the system, as frequently happens during regular maintenance or system
upgrades, nor can active backplane data be disturbed.
GTLP devices fully support live insertion with I
off
, PU3S, and BIAS V
CC
circuitry.
BIAS V
CC
circuitry allows easy internal precharging of the daughter-card backplane
connections to mid-threshold levels to prevent glitching active data during card insertion or
removal.
In the typical connection sequence shown in Figure 15, the GND and BIAS V
CC
connections
are made first to establish the GND plane and precharge the GTLP I/Os through the BIAS
V
CC
circuitry to the 1.0-V ±50-mV threshold voltage. Next, the GTLP I/O pins are connected.
Because the outputs are precharged to 1.0-V before connecting with the backplane, they do
not glitch any active backplane data as they are mated. Finally, V
CC
is connected. As V
CC
ramps up, the BIAS V
CC
precharge circuitry is disabled and the device starts operating,
presenting valid signals on the backplane.
V
CC
GND
I/O
BIAS V
CC
Precharge
Circuit
Output
Stage
V
CC
I/O
BIAS V
CC
GND
Socket
Pins
V
CC
V
CC
Figure 15. Typical BIAS V
CC
Connection Sequence