Datasheet

Product data sheet Rev. 03 — 3 December 2008 6 of 23

NXP Semiconductors

PCA9518A

Expandable 5-channel I

C-bus hub

Standard-mode devices and multiple masters are possible. Please see application note

AN255, I

C/SMBus Repeaters, Hubs and Expanders

for additional information on sizing

resistors.

7. Application design-in information

A typical application is shown in Figure 5. In this example, the system master is running

on a 3.3 V I

C-bus while the slaves are connected to a 3.3 V or 5 V bus. All buses run at

100 kHz unless slave 3, slave 4 and slave 5 are isolated from the bus. Then the master

bus and slave 1, slave 2 and slave 6 can run at 400 kHz.

Any segment of the hub can talk to any other segment of the hub. Bus masters and slaves

can be located on any segment with 400 pF load allowed on each segment.

The PCA9518A is 5 V tolerant, so it does not require any additional circuitry to translate

between the different bus voltages.

When one port of the PCA9518A is pulled LOW by a device on the I

C-bus, a CMOS

hysteresis type input detects the falling edge and drives the EXPxxx1 line LOW, when the

EXPxxx1 voltage is less than 0.5V

, the other ports are pulled down to the V

of the

PCA9518A which is typically 0.5 V.