PCA9507D datasheet(8/20 Pages) NXP

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PCA9507_1

Product data sheet

Rev. 01 — 7 February 2008

8 of 20

NXP Semiconductors

PCA9507

2-wire serial bus extender for HDMI DDC I2C-bus and SMBus

According to Figure 6, when port A of the PCA9507 is pulled LOW by a driver on the

I2C-bus, a comparator detects the falling edge when it goes below 0.3VCC(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 I2C-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 VCC(B) as it sends data to the slave

at the falling edge of the 8th 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 9th 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. I2C-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.

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