PCA9545A Datasheet, PDF(1/28 Page) Texas Instruments – 4-CHANNEL I2C AND SMBus SWITCH WITH INTERRUPT LOGIC AND RESET FUNCTIONS

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PCA9545A Datasheet, PDF (1/28 Pages) Texas Instruments – 4-CHANNEL I2C AND SMBus SWITCH WITH INTERRUPT LOGIC AND RESET FUNCTIONS

PCA9545A/45B/45C

4-channel I2C-bus switch with interrupt logic and reset

Rev. 07 â 19 June 2009

Product data sheet

1. General description

The PCA9545A/45B/45C is a quad bidirectional translating switch controlled via the

I2C-bus. The SCL/SDA upstream pair fans out to four downstream pairs, or channels. Any

individual SCx/SDx channel or combination of channels can be selected, determined by

the contents of the programmable control register. Four interrupt inputs, INT0 to INT3, one

for each of the downstream pairs, are provided. One interrupt output, INT, acts as an AND

of the four interrupt inputs.

An active LOW reset input allows the PCA9545A/45B/45C to recover from a situation

where one of the downstream I2C-buses is stuck in a LOW state. Pulling the RESET pin

LOW resets the I2C-bus state machine and causes all the channels to be deselected as

does the internal power-on reset function.

The pass gates of the switches are constructed such that the VDD pin can be used to limit

the maximum high voltage which will be passed by the PCA9545A/45B/45C. This allows

the use of different bus voltages on each pair, so that 1.8 V or 2.5 V or 3.3 V parts can

communicate with 5 V parts without any additional protection. External pull-up resistors

pull the bus up to the desired voltage level for each channel. All I/O pins are 5 V tolerant.

The PCA9545A, PCA9545B and PCA9545C are identical except for the ï¬xed portion of

the slave address.

2. Features

I 1-of-4 bidirectional translating switches

I I2C-bus interface logic; compatible with SMBus standards

I 4 active LOW interrupt inputs

I Active LOW interrupt output

I Active LOW reset input

I 2 address pins allowing up to 4 devices on the I2C-bus

I Alternate address versions A, B and C allow up to a total of 12 devices on the bus for

larger systems or to resolve address conï¬icts

I Channel selection via I2C-bus, in any combination

I Power-up with all switch channels deselected

I Low Ron switches

I Allows voltage level translation between 1.8 V, 2.5 V, 3.3 V and 5 V buses

I No glitch on power-up

I Supports hot insertion

I Low standby current

I Operating power supply voltage range of 2.3 V to 5.5 V

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