Data Sheet

Table Of Contents

Product data sheet Rev. 01 — 7 October 2005 8 of 22

Philips Semiconductors

PCA9512A

Level shifting hot swappable I

C-bus and SMBus bus buffer

8.8 Hot swapping and capacitance buffering application

Figure 7 through Figure 9 illustrate the usage of the PCA9512A in applications that take

advantage of both its hot swapping and capacitance buffering features. In all of these

applications, note that if the I/O cards were plugged directly into the backplane, all of the

backplane and card capacitances would add directly together, making rise time and

fall time requirements difﬁcult to meet. Placing a bus buffer on the edge of each card,

however, isolates the card capacitance from the backplane. For a given I/O card, the

PCA9512A drives the capacitance of everything on the card and the backplane must drive

only the capacitance of the bus buffer, which is less than 10 pF, the connector, trace, and

all additional cards on the backplane.

See

Application Note AN10160, ‘Hot Swap Bus Buffer’

for more information on

applications and technical assistance.

Fig 5. Bus requirements for 3.3 V systems Fig 6. Bus requirements for 5 V systems

(pF)

0 400300100 200

002aab582

(kΩ)

recommended

pull-up

rise time > 300 ns

max

= 24 kΩ