1. General description
The PCA9543A/43B is a bidirectional translating switch, controlled by the I
2
C-bus. The
SCL/SDA upstream pair fans out to two downstream pairs, or channels. Any individual
SCx/SDx channels or combination of channels can be selected, determined by the
contents of the programmable control register. Two interrupt inputs, INT0
and INT1, one
for each of the downstream pairs, are provided. One interrupt output, INT
, which acts as
an AND of the two interrupt inputs, is provided.
An active LOW reset input allows the PCA9543X to recover from a situation where one of
the downstream I
2
C-buses is stuck in a LOW state. Pulling the RESET pin LOW resets
the I
2
C-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 V
DD
pin can be used to limit
the maximum high voltage which will be passed by the PCA9543X. This allows the use of
different bus voltages on each SCx/SDx pair, so that 1.8 V, 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 PCA9543A and PCA9543B are identical except for the fixed portion of the slave
address.
2. Features and benefits
1-of-2 bidirectional translating switches
I
2
C-bus interface logic; compatible with SMBus standards
2 active LOW interrupt inputs
Active LOW interrupt output
Active LOW reset input
2 address pins allowing up to 4 devices on the I
2
C-bus
Alternate address versions A and B allow up to a total of 12 devices on the bus for
larger systems or to resolve address conflicts
Channel selection via I
2
C-bus, in any combination
Power-up with all switch channels deselected
Low R
on
switches
Allows voltage level translation between 1.8 V, 2.5 V, 3.3 V and 5 V buses
No glitch on power-up
Supports hot insertion
Low standby current
Operating power supply voltage range of 2.3 V to 5.5 V
PCA9543A/43B
2-channel I
2
C-bus switch with interrupt logic and reset
Rev. 8 — 3 April 2014 Product data sheet
