Datasheet

PCA9510A_4 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 04 — 18 August 2009 8 of 24
NXP Semiconductors
PCA9510A
Hot swappable I
2
C-bus and SMBus bus buffer
8.8 Hot swapping and capacitance buffering application
Figure 7 through Figure 10 illustrate the usage of the PCA9510A 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
PCA9510A 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.
(1) Unshaded area indicates recommended pull-up.
Fig 5. Bus requirements for 3.3 V systems
(1) Unshaded area indicates recommended pull-up.
Fig 6. Bus requirements for 5 V systems
C
b
(pF)
0 400300200100
002aae778
20
10
30
50
R
PU
(kΩ)
0
R
max
= 45 kΩ
rise time = 20 ns
R
min
= 1 kΩ
rise time = 1000 ns
40
(1)
rise time = 300 ns
C
b
(pF)
0 400300200100
002aae779
70
R
PU
(kΩ)
0
10
20
30
40
50
60
(1)
R
max
= 65.7 kΩ
rise time = 20 ns
R
min
= 1.7 kΩ
rise time = 1000 ns
rise time = 300 ns