LTC4305IGN Linear Technology, LTC4305IGN Datasheet - Page 16

• Manufacturer Part Number: LTC4305IGN
• Description: IC BUFFER BUS 2WR ADDRESS 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC4305IGN

• Applications: Multiplexer with Amplifier
• Interface: SMBus (2-Wire/I²C)
• Voltage - Supply: 2.2 V ~ 5.5 V
• Package / Case: 16-SSOP
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LTC4305
APPLICATIO S I FOR ATIO
16
Level Shifting Considerations
In Figure 5, the LTC4305 V
to both of the downstream bus pull-up voltages, so both
downstream buses can be active at the same time. Like-
wise, the rise time accelerators can be turned on for the
downstream buses, but must never be activated on SCLIN
and SDAIN, because doing so would result in significant
current flow from V
Other Application Circuits
Figure 6 illustrates how the LTC4305 can be used to
expand the number of devices in a system by using nested
addressing. Each I/O card contains a temperature sensor
having device address 1001 000. If both I/O cards were
plugged directly into the backplane, the two sensors
would require two unique addresses. However, if masters
use the LTC4305 in multiplexer mode, where only one
downstream channel is connected at a time, then each
I/O card can have a device with address 1001 000 and no
problems will occur.
Figures 7 and 8 show two different methods for hot-
swapping I/O cards onto a live two-wire bus using the
LTC4305. The circuitry of Figure 7 consists of an LTC4305
residing on the edge of an I/O card having two separate
downstream buses. Connect a 200k resistor to ground
CONTROLLER
MICRO-
U
CC
to V
U
CC
BACK
R1
10k
voltage is less than or equal
during rising edges.
R2
10k
W
V
CC
Figure 6. Nested Addressing Application
OPEN
R3
10k
V
CC
U
R4
10k
11
10
5
3
6
2
9
8
4
SCLIN
SDAIN
ENABLE
ALERT
READY
ADR2
ADR1
ADR0
GND
ADDRESS = 1010 000
LTC4305
7
V
from the ENABLE pin and make the ENABLE pin the
shortest pin on the card connector, so that the ENABLE pin
remains at a constant logic low while all other pins are
connecting. This ensures that the LTC4305 remains in its
default high impedance state and ignores connection
transients on its SDAIN and SCLIN pins until they have
established solid contact with the backplane 2-wire bus.
In addition, make sure that the ALERT card connector pin
is shorter than the V
contact with the I/O card pull-up supply pin and powers
the pull-up resistors on ALERT1–ALERT2 before ALERT
makes contact.
Figure 8 illustrates an alternate SDA and SCL hot-
swapping technique, where the LTC4305 is located on the
backplane and an I/O card plugs into downstream channel
2. Before plugging and unplugging the I/O card, make sure
that channel 2’s downstream switch is open, so that it does
not disturb any 2-wire transaction that may be occurring
at the moment of connection/disconnection. Note that
pull-up resistor R10 on ALERT2 should be located on the
backplane and not the I/O card to ensure proper operation
of the LTC4305 when the I/O card is not present. The pull-
up resistors on SCL2 and SDA2—R8 and R9, respec-
tively—may be located on the I/O card, provided that
downstream bus 2 is never activated when the I/O card is
not present. Otherwise, locate R8 and R9 on the backplane.
CC
ALERT1
ALERT2
SDA1
SDA2
SCL1
SCL2
C1
0.01µF
12
13
14
16
15
1
R5
10k
R8
10k
CC
R6
10k
R9
10k
pin, so that V
R7
10k
R10
10k
ADDRESS = 1001 000
ADDRESS = 1001 000
TEMPERATURE
TEMPERATURE
I/O CARD #1
I/O CARD #2
SENSOR
SENSOR
CC
4305 F06
establishes solid
4305f