LTC4306CGN#PBF Linear Technology, LTC4306CGN#PBF Datasheet - Page 10
![IC MUX 4CH 2-WIRE BUS 24-SSOP](/photos/6/59/65961/161-24-ssop_sml.jpg)
LTC4306CGN#PBF
Manufacturer Part Number
LTC4306CGN#PBF
Description
IC MUX 4CH 2-WIRE BUS 24-SSOP
Manufacturer
Linear Technology
Datasheet
1.LTC4306CUFDPBF.pdf
(20 pages)
Specifications of LTC4306CGN#PBF
Applications
Multiplexer with Amplifier
Interface
SMBus (2-Wire/I²C)
Voltage - Supply
2.2 V ~ 5.5 V
Package / Case
24-SSOP
Mounting Type
Surface Mount
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
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Part Number
Manufacturer
Quantity
Price
OPERATIO
LTC4306
10
The LTC4306 is a 4-channel, 2-wire bus multiplexer/
switch with bus buffers to provide capacitive isolation
between the upstream bus and downstream buses. Mas-
ters on the upstream 2-wire bus (SDAIN and SCLIN) can
command the LTC4306 to any combination of the 4
downstream buses. Masters can also program the LTC4306
to disconnect the upstream bus from the downstream
buses if the bus is stuck low.
Undervoltage Lockout (UVLO) and ENABLE
Functionality
The LTC4306 contains undervoltage lockout circuitry that
maintains all of its SDA, SCL, GPIO and ALERT pins in high
impedance states until the device has sufficient V
voltage to function properly. It also ignores any attempts
to communicate with it via the 2-wire buses in this condi-
tion. When the ENABLE pin voltage is low (below 0.8V), all
control bits are reset to their default high impedance
states, and the LTC4306 ignores 2-wire bus commands.
However, with ENABLE low, the LTC4306 still monitors
the ALERT1-ALERT4 pin voltages and pulls the ALERT pin
low if any of ALERT1-ALERT4 is low. When ENABLE is
high, devices can read from and write to the LTC4306.
Connection Circuitry
Masters on the upstream SDAIN/SCLIN bus can write to
the Bus 1 FET State through Bus 4 FET State bits of register
3 to connect to any combination of downstream channels
1 to 4. By default, the Connection Circuitry shown in the
Block Diagram will only connect to downstream channels
whose corresponding Bus Logic State bits in register 3 are
high at the moment that it receives the connection com-
mand. If the LTC4306 is commanded to connect to mul-
tiple channels at once, it will only connect to the channels
that are high. Masters can override this feature by setting
the Connection Requirement bit of register 2 high. With
this bit high, the LTC4306 executes connection com-
mands without regard to the logic states of the down-
stream channels.
Upon receiving the connection command, the Connec-
tion Circuitry will activate the Upstream-Downstream
Buffers under two conditions: first, the master must be
U
CC
supply
commanding connection to one or more downstream
channels, and second, there must be no stuck low
condition (see Stuck Low Timeout Fault discussion). If
the connection command is successful, the Upstream-
Downstream Buffers pass signals between the upstream
bus and the connected downstream buses. The LTC4306
also turns off its N-channel MOSFET open-drain pull-
down on the READY pin, so that READY can be pulled
high by its external pull-up resistor.
Upstream-Downstream Buffers
Once the Upstream-Downstream Buffers are activated,
the functionality of the SDAIN and any connected down-
stream SDA pins is identical. A low forced on any con-
nected SDA pin at any time results in all pins being low.
External devices must pull the pin voltages below 0.4V
worst-case with respect to the LTC4306’s ground pin to
ensure proper operation. The SDA pins enter a logic high
state only when all devices on all connected SDA pins force
a high. The same is true for SCLIN and the connected
downstream SCL pins. This important feature ensures
that clock stretching, clock arbitration and the acknowl-
edge protocol always work, regardless of how the devices
in the system are connected to the LTC4306.
The Upstream-Downstream Buffers provide capacitive
isolation between SDAIN/SCLIN and the downstream con-
nected buses. Note that there is no capacitive isolation
between connected downstream buses; they are only
separated by the series combination of their switches’ on
resistances.
While any combination of downstream buses may be
connected at the same time, logic high levels are corrupted
if multiple downstream buses are active and both the V
voltage and one or more downstream bus pull-up voltages
are larger than the pull-up supply voltage for another
downsteam bus. An example of this issue is shown in
Figure 1. During logic highs, DC current flows from V
through the series combination of R1, N1, N2 and R2 and
into V
to be sourced into V
activate bus 1 or any other downstream bus whose pull-
up voltage is above 2.5V when bus 2 is active.
BUS2
, causing the SDA1 voltage to drop and current
BUS2
. To avoid this problem, do not
BUS1
4306f
CC