PCA9554 查看數據表（PDF） - Philips Electronics

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PCA9554

8-bit I²C and SMBus I/O port with interrupt

Philips Electronics 

Philips Semiconductors

8-bit I2C and SMBus I/O port with interrupt

Product data sheet

PCA9554/PCA9554A

SIMPLIFIED SCHEMATIC OF I/O0 TO I/O7

DATA FROM

SHIFT REGISTER

DATA FROM

SHIFT REGISTER

WRITE

CONFIGURATION

PULSE

WRITE PULSE

CONFIGURATION

REGISTER

DQ

FF

CK Q

DQ

FF

CK Q

OUTPUT

PORT

REGISTER

READ PULSE

Q1

INPUT PORT

REGISTER

DQ

FF

CK Q

100 kΩ

Q2

DATA FROM

SHIFT REGISTER

WRITE

POLARITY

PULSE

DQ

FF

CK Q

POLARITY

INVERSION

REGISTER

NOTE: At Power-on Reset, all registers return to default values.

Figure 4. Simplified schematic of I/O0 to I/O7

I/O port

When an I/O is configured as an input, FETs Q1 and Q2 are off,

creating a high-impedance input with a weak pull-up (100 kΩ typ.) to

VDD. The input voltage may be raised above VDD to a maximum of

5.5 V.

If the I/O is configured as an output, then either Q1 or Q2 is enabled,

depending on the state of the output port register. Care should be

exercised if an external voltage is applied to an I/O configured as an

output because of the low impedance paths that exist between the

pin and either VDD or VSS.

OUTPUT PORT

REGISTER DATA

VDD

I/O0 TO I/O7

VSS

INPUT PORT

REGISTER DATA

TO INT

POLARITY

REGISTER DATA

SU01472

2004 Sep 30

6

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