CAT9554A Datasheet, PDF (6/16 Pages) Catalyst Semiconductor – 8-bit I2C and SMBus I/O Port with Interrupt

CAT9554, CAT9554A
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 Vcc. 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 CAT9554/9554As 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/O₀ to I/O₇: 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 100
kΩ). 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 Value versus
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.
Doc. No. 25088, Rev. B
6
© 2006 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice