September 2006
rev 1.1
T
J
,MAX should be selected according to the MTBF
system requirements and Table 11. R
thja
can be derived
from Table 12. The R
thja
represent data based on 1S2P
boards, using 2S2P boards will result in a lower thermal
impedance than indicated below.
PCS2I9940L
If the calculated maximum frequency is below 250MHz, it
becomes the upper clock speed limit for the given
application conditions. The following eight derating charts
describe the safe frequency operation range for the
PCS2I9940L. The charts were calculated for a maximum
tolerable die junction temperature of 110°C (120°C),
corresponding to an estimated MTBF of 9.1 years
(4 years), a supply voltage of 3.3V and series terminated
transmission line or capacitive loading. Depending on a
given set of these operating conditions and the available
device convection a decision on the maximum operating
frequency can be made.
Table 12. Thermal package impedance of the
32LQFP
Convection,
R
thja
(1P2S
R
thja
(2P2S
board),
°C/W
board),
°C/W
LFPM
Still air
100 lfpm
200 lfpm
300 lfpm
400 lfpm
500 lfpm
86
76
71
68
66
60
61
56
54
53
52
49
Low Voltage 1:18 Clock Distribution Chip
Notice: The information in this document is subject to change without notice.
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