1. General description
The PCA9545A/45B/45C is a quad bidirectional translating switch controlled via the
I
2
C-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 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 is 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 fixed portion of
the slave address.
2. Features and benefits
1-of-4 bidirectional translating switches
I
2
C-bus interface logic; compatible with SMBus standards
4 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, B and C 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
PCA9545A/45B/45C
4-channel I
2
C-bus switch with interrupt logic and reset
Rev. 9 — 5 May 2014 Product data sheet
