PCA9512A_1
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Product data sheet
Rev. 01 — 7 October 2005
8 of 22
Philips Semiconductors
PCA9512A
Level shifting hot swappable I2C-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
Cb (pF)
0
400
300
100
200
002aab582
10
20
30
RPU
(k
Ω)
0
recommended
pull-up
rise time > 300 ns
Rmax = 24 kΩ
Cb (pF)
0
400
300
100
200
002aab583
10
5
15
20
RPU
(k
Ω)
0
recommended
pull-up
rise time > 300 ns
Rmax = 16 kΩ
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