TCA9555 Datasheet, PDF (5/32 Pages) Texas Instruments – LOW VOLTAGE 16-BIT I2C AND SMBus I/O EXPANDER WITH INTERRUPT OUTPUT AND CONFIGURATION REGISTERS

TCA9555
www.ti.com .............................................................................................................................................................. SCPS200A – JULY 2009 – REVISED JULY 2009
SIMPLIFIED SCHEMATIC OF P-PORT I/Os
Data From
Shift Register
Data From
Shift Register
Write Configuration
Pulse
Write Pulse
Configuration
Register
DQ
FF
CLK Q
DQ
FF
CLK Q
Output Port
Register
Read Pulse
Output Port
Register Data
V_CC
Q1
100 kW
Input Port
Register
DQ
FF
CLK Q
I/O Pin
Q2
GND
Input Port
Register Data
To INT
Data From
Shift Register
Write Polarity
Pulse
DQ
FF
CLK Q
Polarity Inversion
Register
Polarity
Register Data
I/O Port
When an I/O is configured as an input, FETs Q1 and Q2 are off, creating a high-impedance input. The input
voltage may be raised above V_CC to a maximum of 5.5 V.
If the I/O is configured as an output, Q1 or Q2 is enabled, depending on the state of the Output Port register. In
this case, there are low-impedance paths between the I/O pin and either V_CC or GND. The external voltage
applied to this I/O pin should not exceed the recommended levels for proper operation.
Copyright © 2009, Texas Instruments Incorporated
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