LTC4302-1/LTC4302-2
5
sn430212 430212fs
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PI FU CTIO S
SDAIN (Pin 1): Serial Data Input. Connect this pin to the
SDA bus on the backplane. Do not float.
SCLIN (Pin 2): Serial Clock Input. Connect this pin to the
SCL bus on the backplane. Do not float.
CONN (Pin 3): Register Reset and Connection Sense
Input. Driving this pin low resets the registers to their
default state: GPIOs in output open-drain high impedance
mode, rise time accelerators disabled and the input-to-
output connection disabled. Communication with the
LTC4302-1/LTC4302-2 is disabled when CONN is low.
When CONN is brought back high, the registers remain in
the default state and communication is enabled.
ADDRESS (Pin 4): 2-Wire Address Programming Input.
The 2-wire address is programmed by connecting
ADDRESS to a resistive divider between V
CC
and ground.
The voltage on ADDRESS is converted by an internal
analog-to-digital (A/D) converter into a 5-bit digital word.
This resulting digital code represents the least significant
five bits of the 2-wire address. 1% resistors must be used
to ensure accurate address programming. 32 unique
addresses are possible. See Table 1 for 1% resistor values
and corresponding addresses. Care must also be taken to
minimize capacitance on ADDRESS. Resistors must be
placed close to the LTC4302-1/LTC4302-2’s V
CC
, GND
and ADDRESS pins.
GND (Pin 5): Ground. Connect this pin to a ground plane
for best results.
GPIO1 (Pin 6): General Purpose Input/Output (GPIO1).
GPIO1 can be used as an input, an open-drain output or a
push-pull output. The N-Channel MOSFET pulldown de-
vice is capable of driving LEDs. When used in input or
open-drain output mode, the I/O pin can be pulled up to a
supply voltage ranging from 2.2V to 5.5V independent of
the V
CC
voltage.
GPIO2 (Pin 7, LTC4302-1): General Purpose Input/Out-
put. GPIO2 can be used as an input, an open-drain output,
or a push-pull output. The N-Channel MOSFET pulldown
device is capable of driving LED’s. When used in input or
open-drain output mode, the I/O pin can be pulled up to a
supply voltage ranging from 2.2V to 5.5V independent of
the V
CC
voltage.
V
CC2
(Pin 7, LTC4302-2): Card Side Supply Voltage. This
pin is a power supply pin for the card side busses. Connect
V
CC2
to the card’s V
CC
and connect a bypass capacitor of
at least 0.01µF directly between V
CC2
and GND for best
results.
V
CC
(Pin 8): Main Input Power Supply from Backplane.
Connect a bypass capacitor of at least 0.01µF directly
between V
CC
and GND for best results.
SCLOUT (Pin 9): Serial Clock Output. Connect this pin to
the SCL bus on the I/O card. Do not float.
SDAOUT (Pin 10): Serial Data Output. Connect this pin to
the SDA bus on the I/O card. Do not float.
t
SU, DAT
t
SU, STO
t
SU, STA
t
BUF
t
HD, STA
t
SP
t
SP
t
HD, DATO,
t
HD, DATI
t
HD, STA
t
f
START
CONDITION
STOP
CONDITION
REPEATED START
CONDITION
START
CONDITION
4302 TD01
SDA
SCL
TI I G DIAGRA
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