Datasheet

LTC4300A-1/LTC4300A-2
5
4300a12fa
PIN FUNCTIONS
ENABLE/V
CC2
(Pin 1): Chip Enable Pin/Card Supply Volt-
age. For the LTC4300A-1, this is a digital CMOS threshold
input pin. Grounding this pin puts the part in a low current
(<1μA) mode. It also disables the rise-time accelerators,
disables the bus precharge circuitry, drives READY low,
isolates SDAIN from SDAOUT and isolates SCLIN from
SCLOUT. Drive ENABLE all the way to V
CC
for normal
operation. Connect ENABLE to V
CC
if this feature is not
being used. For the LTC4300A-2, this is the supply voltage
for the devices on the card I
2
C busses. Connect pull-up
resistors from SDAOUT and SCLOUT to this pin. Place a
bypass capacitor of at least 0.01μF close to this pin for
best results.
SCLOUT (Pin 2): Serial Clock Output. Connect this pin to
the SCL bus on the card.
SCLIN (Pin 3): Serial Clock Input. Connect this pin to the
SCL bus on the backplane.
GND (Pin 4): Ground. Connect this pin to a ground plane
for best results.
READY/ACC (Pin 5): Connection Flag/Rise-Time Accelera-
tor Control. For the LTC4300A-1, this is an open-drain
NMOS output which pulls low when either ENABLE is
low or the start-up sequence described in the Operation
section has not been completed. READY goes high when
ENABLE is high and start-up is complete. Connect a 10k
resistor from this pin to V
CC
to provide the pull up. For
the LTC4300A-2, this is a CMOS threshold digital input
pin that enables and disables the rise-time accelerators
on all four SDA and SCL pins. Drive ACC all the way to the
V
CC2
supply voltage to enable all four accelerators; drive
ACC to ground to turn them off.
SDAIN (Pin 6): Serial Data Input. Connect this pin to the
SDA bus on the backplane.
SDAOUT (Pin 7): Serial Data Output. Connect this pin to
the SDA bus on the card.
V
CC
(Pin 8): Main Input Power Supply from Backplane.
This is the supply voltage for the devices on the back-
plane I
2
C busses. Connect pull-up resistors from SDAIN
and SCLIN (and also from SDAOUT and SCLOUT for the
LTC4300A-1) to this pin. Place a bypass capacitor of at
least 0.01μF close to this pin for best results.