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ADG3241
Rev. B | Page 13 of 16
CARD I/O
RAM
CPU
AD
G3
241
ADG
3
2
4
1
PLUG-IN
CARD (1)
PLUG-IN
CARD (2)
BUS
04
221
-03
5
1.8V
0V
3.3V
VOUT
SW
IT
C
H
OU
T
P
U
T
SWITCH
INPUT
VIN
3.3V SUPPLY
SEL = 0V
0422
1-
033
SEL
Figure 33. 3.3 V to 1.8 V Voltage Translation,
= 0 V
Figure 35. ADG3241 in a Hot Plug Application
BUS ISOLATION
A common requirement of bus architectures is low capacitance
loading of the bus. Such systems require bus bridge devices that
extend the number of loads on the bus without exceeding the
specifications. Because the ADG3241 is designed specifically for
applications that do not need drive yet require simple logic
functions, it solves this requirement. The device isolates access
to the bus, thus minimizing capacitance loading.
There are many systems, such as docking stations, PCI boards
for servers, and line cards for telecommunications switches, that
require the ability to handle hot swapping. If the bus can be
isolated prior to insertion or removal, there is more control over
the hot swap event. This isolation can be achieved using bus
switches. The bus switches are positioned on the hot swap card
between the connector and the devices. During hot swap, the
ground pin of the hot swap card must connect to the ground
pin of the backplane before any other signal or power pins.
BUS SWITCH
LOCATION
BUS/
BACKPLANE
LOAD A
LOAD C
LOAD B
LOAD D
042
21-
0
34
ANALOG SWITCHING
Bus switches can be used in many analog switching
applications, such as video graphics. Bus switches can have
lower on resistance, smaller on and off channel capacitance, and
thus improved frequency performance over their analog
counterparts.
Figure 34. Location of Bus Switched in a Bus Isolation Application
HOT PLUG AND HOT SWAP ISOLATION
The ADG3241 is suitable for hot swap and hot plug
applications. The output signal of the ADG3241 is limited to a
voltage that is below the VCC supply, as shown in
The bus switch channel itself, consisting solely of an NMOS
switch, limits the operating voltage (see
Figure 4 for a typical
plot), but in many cases this does not present an issue.
to take the impact from hot insertion, protecting vital and
expensive chipsets from damage.
HIGH IMPEDANCE DURING POWER-UP/POWER-
DOWN
To ensure the high impedance state during power-up or power-
down,
In hot plug applications, the system cannot be shut down when
new hardware is being added. To overcome this, a bus switch
can be positioned on the backplane between the bus devices
and the hot plug connectors. The bus switch is turned off
during hot plug.
BE should be tied to VCC through a pull-up resistor; the
minimum value of the resistor is determined by the current-
sinking capability of the driver.
Figure 35 shows a typical example of this type
of application.