CAT9555 Datasheet, PDF (7/18 Pages) Catalyst Semiconductor – 16-bit I2C and SMBus I/O Port with Interrupt

CAT9555
PIN DESCRIPTION
SCL: Serial Clock
The serial clock input clocks all data transferred into
or out of the device. The SCL line requires a pull-up
resistor if it is driven by an open drain output.
SDA: Serial Data/Address
The bidirectional serial data/address pin is used to
transfer all data into and out of the device. The SDA
pin is an open drain output and can be wire-ORed
with other open drain or open collector outputs. A pull-
up resistor must be connected from SDA line to V_CC.
The value of the pull-up resistor, R_P, can be calculated
based on minimum and maximum values from Figure
2 and Figure 3 (see Note).
A0, A1, A2: Device Address Inputs
These inputs are used for extended addressing
capability. The A0, A1, A2 pins should be hardwired to
V_CC or V_SS. When hardwired, up to eight CAT9555s
may be addressed on a single bus system. The levels
on these inputs are compared with corresponding bits,
A2, A1, A0, from the slave address byte.
I/O_0.0 to I/O_0.7, I/O_1.0 to I/O_1.7: Input / Output Ports
Any of these pins may be configured as input or
output. The simplified schematic of I/O₀ to I/O₇ is
shown in Figure 4. When an I/O is configured as an
input, the Q1 and Q2 output transistors are off
creating a high impedance input with a weak pull-up
resistor (typical 100kΩ). If the I/O pin is configured as
an output, the push-pull output stage is enabled. Care
should be taken if an external voltage is applied to an
I/O pin configured as an output due to the low
impedance paths that exist between the pin and either
V_CC or V_SS.
IOL = 3mA @ VOLmax
2.5
2
1.5
1
0.5
0
2 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6
VCC (V)
Fast Mode I²C Bus / tr max - 300ns
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
50 100 150 200 250 300 350 400
CBUS (pF)
Figure 2. Minimum R_P as a Function of
Supply Voltage
Figure 3. Maximum R_P Value versus
Bus Capacitance
Note: According to the Fast Mode I²C bus specification, for bus capacitance up to 200pF, the pull up device can
be a resistor. For bus loads between 200pF and 400pF, the pull-up device can be a current source (Imax = 3mA)
or a switched resistor circuit.
© 2010 SCILLC. All rights reserved
7
Characteristics subject to change without notice
Doc. No. MD-9003, Rev. J