PCA9554 查看數據表（PDF） - ON Semiconductor

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PCA9554

8-bit I2C and SMBus I/O Port with Interrupt

ON Semiconductor 

PCA9554

tF

tHIGH

tR

tLOW

tLOW

SCL

tSU:STA

SDA IN

tHD:STA

tHD:DAT

tSU:DAT

SDA OUT

tAA

tDH

tSU:STO

tBUF

Figure 2. I2C Serial Interface Timing

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, RP,

can be calculated based on minimum and maximum values

from Figure 3 and Figure 4 (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 VCC or VSS.

When hardwired, up to eight PCA9554s 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 5. 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 kW). 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 VCC

or VSS.

2.5

IOL = 3 mA @ VOLmax

2.0

8

7

Fast Mode I2C Bus /

tr max − 300 ns

6

1.5

5

4

1.0

3

2

0.5

1

0

2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.2 5.6

0

0 50 100 150 200 250 300 350 400

VCC (V)

CBUS (pF)

NOTE:

Figure 3. Minimum RP Value vs.

Supply Voltage

Figure 4. Maximum RP Value vs.

Bus Capacitance

According to the Fast Mode I2C bus specification, for bus capacitance up to 200 pF, the pull up device can be a resistor. For bus

loads between 200 pF and 400 pF, the pull−up device can be a current source (Imax = 3 mA) or a switched resistor circuit.

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