TCA9534_16 Datasheet, PDF (14/38 Pages) Texas Instruments – Low Voltage 8-Bit I2C and SMBUS Low-Power I/O Expander with Interrupt Output and Configuration Registers

TCA9534
SCPS197B – SEPTEMBER 2014 – REVISED NOVEMBER 2016
8 Detailed Description
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8.1 Overview
The TCA9534 is an 8-bit I/O expander for the two-line bidirectional bus (I²C) is designed for 1.65-V to 5.5-V V_CC
operation. It provides general-purpose remote I/O expansion for most micro-controller families via the I²C
interface (serial clock, SCL, and serial data, SDA, pins).
The TCA9534 open-drain interrupt (INT) output is activated when any input state differs from its corresponding
Input Port register state and is used to indicate to the system master that an input state has changed. The INT
pin can be connected to the interrupt input of a micro-controller. By sending an interrupt signal on this line, the
remote I/O can inform the micro-controller if there is incoming data on its ports without having to communicate
via the I²C bus. Thus, the TCA9534 can remain a simple slave device. The device outputs (latched) have high-
current drive capability for directly driving LEDs.
Three hardware pins (A0, A1, and A2) are used to program and vary the fixed I²C slave address and allow up to
eight devices to share the same I²C bus or SMBus.
The system master can reset the TCA9534 in the event of a timeout or other improper operation by cycling the
power supply and causing a power-on reset (POR). A reset puts the registers in their default state and initializes
the I²C/SMBus state machine.
The TCA9534 consists of one 8-bit Configuration (input or output selection), Input Port, Output Port, and Polarity
Inversion (active high or active low) registers. At power on, the I/Os are configured as inputs. However, the
system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for
each input or output is kept in the corresponding Input Port or Output Port register. The polarity of the Input Port
register can be inverted with the Polarity Inversion register. All registers can be read by the system master.
The TCA9534 is identical to the TCA9554 except for the removal of the internal I/O pull-up resistors, which
greatly reduces power consumption when the I/Os are held LOW.
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