PCA9507_1 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 01 — 7 February 2008 8 of 20
NXP Semiconductors
PCA9507
2-wire serial bus extender for HDMI DDC I
2
C-bus and SMBus
According to Figure 6, when port A of the PCA9507 is pulled LOW by a driver on the
I
2
C-bus, a comparator detects the falling edge when it goes below 0.3V
CC(A)
and causes
the internal driver on port B to turn on, causing port B to pull down to about 0.5 V. When
port B of the PCA9507 falls, first a CMOS hysteresis type input detects the falling edge
and causes the internal driver on port A to turn on and pull the port A pin down to ground.
In order to illustrate what would be seen in a typical application, refer to Figure 11 and
Figure 12.
If the bus master in Figure 6 were to write to the slave through the PCA9507, waveforms
shown in Figure 11 would be observed on the A bus. This looks like a normal I
2
C-bus
transmission except that the HIGH level may be as low as 2.7 V, and the turn on and turn
off of the acknowledge signals are slightly delayed.
The master drives the B bus to ground or lets it float to V
CC(B)
as it sends data to the slave
at the falling edge of the 8
th
clock, master releases SDAB on the B bus and slave pulls
SDAA on the A bus to ground, causing the PCA9507 to pull SDAB on the B bus to 0.5 V.
At the falling edge of the 9
th
clock, the master again drives the B bus and slave releases
the A bus.
Multiple PCA9507 port A sides can be connected in a star configuration (Figure 9),
allowing all nodes to communicate with each other.
Multiple PCA9507s can be connected in series (Figure 10) as long as port A is connected
to port B. I
2
C-bus slave devices can be connected to any of the bus segments. The
number of devices that can be connected in series is limited by repeater
delay/time-of-flight considerations on the maximum bus speed requirements.
