LTC4306
4306f
6
UU
U
PI FU CTIO S
(GN24 Package/UFD24 Package)
ALERT (Pin 3/Pin 1): Fault Alert Output. An open-drain
output that is pulled low when a fault occurs to alert the
host controller. The LTC4306 pulls ALERT low when any
of the ALERT1-ALERT4 pins is low, when the 2-wire bus
is stuck low, or when the Connection Requirement bit of
Register 2 is low and a master tries to connect to a
downstream channel that is low. See Operation section for
the details of how ALERT is set and cleared. The LTC4306
is compatible with the SMBus Alert Response Address
protocol. Connect a 10k resistor to a power supply voltage
to provide the pull-up. Tie to ground if unused.
SDAIN (Pin 4/Pin 2): Serial Bus Data Input and Output.
Connect this pin to the SDA line on the master side. An
external pull-up resistor or current source is required.
GND (Pin 5/Pin 3): Device Ground.
SCLIN (Pin 6/Pin 4): Serial Bus Clock Input. Connect this
pin to the SCL line on the master side. An external pull-up
resistor or current source is required.
ENABLE (Pin 7/Pin 5): Digital Interface Enable and Regis-
ter Reset. Driving ENABLE high enables I
2
C communica-
tion to the LTC4306. Driving this pin low disables I
2
C
communication to the LTC4306 and resets the registers to
their default state as shown in the Operation section.
When ENABLE returns high, masters can read and write
the LTC4306 again. If unused, tie ENABLE to V
CC
.
V
CC
(Pin 8/Pin 6): Power Supply Voltage. Connect a
bypass capacitor of at least 0.01µF directly between V
CC
and GND for best results.
GPIO1-GPIO2 (Pins 10, 11/Pins 8, 9): General Purpose
Input/Output. These two pins can be used as logic inputs,
open-drain outputs or push-pull outputs. The N-channel
MOSFET pull-down devices are capable of driving LEDs.
When used in input or open-drain output mode, the GPIOs
can be pulled up to a supply voltage ranging from 1.5V to
5.5V independent of the V
CC
voltage. GPIOs default to a
high impedance open-drain output mode. There are GPIO
configuration and status bits in Register 1 and Register 2.
Float if unused.
ADR0-ADR2 (Pins 12, 13, 14/Pins 10, 11, 12): Three-
State Serial Bus Address Inputs. Each pin may be floated,
tied to ground or tied to V
CC
. There are therefore 27
possible addresses. See Table 1 in applications informa-
tion. When the pins are floated, they can tolerate ±5µA of
leakage current and still convert the address correctly.
READY (Pin 15/Pin 13): Connection Ready Digital Output.
An N-channel MOSFET open-drain output transistor that
pulls down when none of the downstream channels is
connected to the upstream bus and turns off when one or
more downstream channels is connected to the upstream
bus. Connect a 10k resistor to a power supply voltage to
provide the pull-up. Tie to ground if unused.
SCL1-SCL4 (Pins 18, 23, 1, 17/Pins 16, 21, 23, 15):
Serial Bus Clock Outputs Channels 1-4. Connect pins
SCL1-SCL4 to the SCL lines on the downstream
channels 1-4, respectively. It is acceptable to float any pin
that will never be connected to the upstream bus. Other-
wise, an external pull-up resistor or current source is
required on each pin.
SDA1-SDA4 (Pins 19, 22, 2, 16/Pins 17, 20, 24, 14):
Serial Bus Data Output Channels 1-4. Connect pins
SDA1-SDA4 to the SDA lines on downstream channels
1-4, respectively. It is acceptable to float any pin that will
never be connected to the upstream bus. Otherwise, an
external pull-up resistor or current source is required on
each pin.
ALERT1-ALERT4 (Pins 20, 24, 21, 9/Pins 18, 22,
19, 7): Fault Alert Inputs, Channels 1-4. Devices on each
of the four output channels can pull their respective pin
low to indicate that a fault has occurred. The LTC4306 then
pulls the ALERT low to pass the fault indication on to the
host. See Operation section below for the details of how
ALERT is set and cleared. Connect unused fault alert
inputs to V
CC
.
Exposed Pad (Pin 25, UFD Package Only): Power Ground.
Exposed Pad may be left open or connected to device
ground.
