Datasheet
9
LTC4301
4301fb
filter to prevent the LTC4301 from becoming activated
until the transients associated with live insertion have
settled. Connect the capacitor between V
CC
and CS, and
the resistor from CS to GND.
Repeater/Bus Extender Application
Users who wish to connect two 2-wire systems separated
by a distance can do so by connecting two LTC4301s
back-to-back as shown in Figure 6. The I
2
C specification
allows for 400pF maximum bus capacitance, severely
limiting the length of the bus. The SMBus specification
places no restriction on bus capacitance, but the limited
impedances of devices connected to the bus require
systems to remain small if rise- and fall-time specifica-
tions are to be met. Using the LTC4301 allows the capaci-
tance to be isolated into smaller sections, enabling the
APPLICATIO S I FOR ATIO
WUUU
R3
100k
SDAIN
SCLIN
V
CC
GND
SDAOUT
SCLOUT
READY
CS
SDAIN
SCLIN
V
CC
GND
SDAOUT
SCLOUT
READY
4301 F05
R9
10k
R8
10k
R10
10k
I/O PERIPHERAL CARD 2
LTC4301
CARD2_SCL
CARD2_SDA
R5
10k
R4
10k
I/O PERIPHERAL CARD 1
LTC4301
CARD_SCL
CARD_SDA
R1
10k
V
CC
V
CC2
R2
10k
BACKPLANE
BACKPLANE
CONNECTOR
SDA
SCL
0.01µF
0.1µF
0.01µF
R6
10k
•
•
•
R7
100k
CS
0.1µF
system to meet rise- and fall-time requirements. In this
situation, the differential ground voltage between the two
systems may limit the allowed distance, because valid
logic low voltage with respect to the ground at one end of
the system may violate the allowed V
OL
specification with
respect to the ground at the other end. In addition, the
connection circuitry offset voltages of the back-to-back
LTC4301s add together, directly contributing to the same
problem.
Systems with Supply Voltage Droop
In large 2-wire systems, the V
CC
voltages seen by devices
at various points in the system can differ by a few hundred
millivolts or more. This situation is well modelled by a series
resistor in the V
CC
line as shown in Figure 7. For proper
operation, make sure that the V
CC(LTC4301)
is ≥ 2.7V.
Figure 5. Inserting Multiple I/O Cards into a Live Backplane Using the LTC4301 in a PCI System