2
AN1543.0
April 1, 2010
ISL3300x Buffers
The ISL33001, ISL33002, ISL33003 family of 2-Channel
Bus Buffers are designed to isolate the bus capacitance
and improve the rise time performance of heavily loaded
buses. The family of buffers offer +2.3V to +5.5V
operation, hot swap capability, transient rise time
accelerators, low power shutdown (ISL33001 and
ISL33003) and level shifting capability (ISL33002 and
ISL33003).
The buffers are designed to operate in wired-AND
environments such as I
2
C bus, supporting 400kHz Fast
Mode operation while being capable of driving the I
2
C
specified maximum capacitive loads of 400pF on the bus.
Power Supply
The ISL3300xMSOPEVAL1Z boards required a +2.3V to
+5.5V supply voltage to power the ISL3300x IC. For
ISL33002 and ISL33003 with level shifting power
supplies, a supply voltage in the +2.3V to +5.5V must be
connected to the V
CC1
and V
CC2
banana jack
connections. The evaluation board contains 0.01µF local
decoupling capacitor near the supply pins of the
ISL3300x IC.
Note: Jumper J4 connects either banana jack EN/V
CC2
or
BNC connector EN/V
CC2
to pin 1 of the ISL3300x IC.
When the jumper is in the 1-2 position the connection is
made to the banana jack. When in the 2-3 position the
connection is made to the BNC connector.
Logic Control Inputs
ISL33001
The ISL33001 device contains an enable logic input pin
“EN” and a logic output pin “READY”.
The enable pin connection can be made at the banana
jack or BNC connector. When the EN pin is driven high,
the part is enabled and the buffer will be connected once
it enters a valid state. When the EN pin is driven low, the
part is disabled, the IC draws low ICC current and any
signals on one side of the buffer will not appear on the
other side of the buffer.
Note: Jumper J4 connects either banana jack EN/V
CC2
or
BNC connector EN/V
CC2
to pin 1 (EN) of the ISL33001
IC. When the jumper is in the 1-2 position the connection
is made to the banana jack. When in the 2-3 position the
connection is made to the BNC connector.
The READY pin is an Open-Drain logic output pin on the
ISL33001 IC. The evaluation board gives the option to
connect the READY pin to a 10kΩ pull-up resistor to V
CC1
or to an external connector.
Note: Jumper J21 connects either the 10kΩ pull-up
resistor or the external connector to pin 4 (READY) on
the ISL33001 IC. When J21 is in the 1-2 position the
READY pin is connected to the 10kΩ pull-up resistor.
When J21 is in the 2-3 position the READY pin is
connected commonly to banana jack EN/READY/ACC and
BNC connector JEN/READY/ACC.
ISL33002
The ISL33002 device contains a level shifting supply
voltage V
CC2
and an Accelerator disable pin ACC.
The V
CC2
connection can be made at the banana jack
EN/V
CC2
. For the ISL33002 IC, the threshold voltages on
the SDA_OUT and SCL_OUT pins are referred to the
V
CC2
supply.
Note: Jumper J4 connects either banana jack EN/V
CC2
or
BNC connector EN/V
CC2
to pin 1 (V
CC2
) of the ISL33002
IC. When the jumper is in the 1-2 position the connection
is made to the banana jack. When in the 2-3 position the
connection is made to the BNC connector.
Note: Jumper J2 connects the pull-up resistors on the
SDA_OUT and SCL_OUT pins to either the V
CC1
or V
CC2
supply. When J2 is in the 1-2 position the pull-up
resistors are connected to V
CC2
. When J2 is in the 2-3
position the pull-up resistors are connected to V
CC2
.
The ACC pin is a logic input pin that enables/disables the
bus accelerators on the ISL33002 IC SDA/SCL pins. The
evaluation board gives the option to connect the ACC pin
to a 10kΩ pull-up resistor to V
CC1
to enabled the
accelerators at all times or to banana jack/BNC
connectors for external control.
Jumper J21 connects either the 10kΩ pull-up resistor or
the external connector to pin 4 (ACC) on the ISL33002
IC. When J21 is in the 1-2 position the ACC pin is
connected to the 10kΩ pull-up resistor. When J21 is in
the 2-3 position the ACC pin is connected commonly to
banana jack EN/READY/ACC and BNC connector
JEN/READY/ACC.
ISL33003
The ISL33003 device contains a level shifting supply
voltage V
CC2
and an enable logic input pin EN.
The V
CC2
connection can be made at the banana jack
EN/V
CC2
. For the ISL33003 IC, the threshold voltages on
the SDA_OUT and SCL_OUT pins are referred to the
V
CC2
supply.
Note: Jumper J4 connects either banana jack EN/V
CC2
or
BNC connector EN/V
CC2
to pin 1 (V
CC2
) of the ISL33003
IC. When the jumper is in the 1-2 position the connection
is made to the banana jack. When in the 2-3 position the
connection is made to the BNC connector.
Note: Jumper J2 connects the pull-up resistors on the
SDA_OUT and SCL_OUT pins to either the V
CC1
or
V
CC2
supply. When J2 is in the 1-2 position the pull-up
resistors are connected to V
CC2
. When J2 is in the 2-3
position the pull-up resistors are connected to V
CC2
.
SDA/SCL Pins
To include the features to evaluate the ISL3300x buffers
on the evaluation board, the necessary components are
available to interface with a 2-Channel wired-AND bus
such as I
2
C.
The I
2
C bus utilizes an active pull-down circuit to drive a
low on the bus and a pull-up resistor to passively pull the
Application Note 1543