ispPAC-CLK55xx Lattice Semiconductor, ispPAC-CLK55xx Datasheet - Page 24

• Manufacturer Part Number: ispPAC-CLK55xx
• Description: In-System Programmable Clock Generator with Universal Fan-Out Buffer
• Manufacturer: Lattice Semiconductor

Lattice Semiconductor
With a maximum recommended operating junction temperature (T
maximum allowable ambient temperature (T
where Θ
The above analysis represents the worst-case scenario. Significant improvement in maximum ambient operating
temperature can be realized with additional cooling. Providing a 200 LFM (Linear Feet per Minute) airflow reduces
Θ
In practice, however, the absolute worst-case situation will be relatively rare, as not all outputs may be running at
maximum output frequency in a given application. Additionally, if the internal VCO is operating at less than its max-
imum frequency (640MHz), it requires less current on the VCCD pin. In these situations, one can estimate the
effective I
VCO frequency. Normalized curves relating current to operating frequency for these parameters may be found in
the Typical Performance Characteristics section.
While it is possible to perform detailed calculations to estimate the maximum ambient operating temperature from
operating conditions, some simpler rule-of-thumb guidance can also be obtained through the derating curves
shown in Figure 22. The curves in Figure 22a show the maximum ambient operating temperature permitted when
operating a given number of output banks at the maximum output frequency (320MHz). Note that it is assumed that
both outputs in each bank are active.
Figure 22. Maximum Ambient Temperature vs. Number of Active Output Banks
JA
to 29°C/W, which results in a maximum ambient operating temperature of 66°C.
JA
CCO
= 35 °C/W in still air for the ispClock5520’s TQFP100 package.
for each bank and the effective I
90
80
70
60
50
40
90
80
70
60
50
40
0
(Outputs LVCMOS 3.3V, f
0
T
(Outputs LVDS, f
Temperature Derating Curves
Temperature Derating Curves
AMAX
2
2
# Active Output Banks
# Active Output Banks
= T
4
4
JOP
(c)
(a)
- PD
OUT
6
6
=320 MHz)
OUT
AMAX
MAX
=320 MHz)
CCD
8
8
x Θ
) can be estimated as
JA
for the digital core functions based on output frequency and
10
10
= 115°C - 1.67W x 35°C/W = 56°C
24
90
80
70
60
50
40
0
(Outputs LVCMOS 3.3V, f
JOP
Temperature Derating Curves
5520 Commercial
5520 Industrial
5510 Commericial
5510 Industrial
) of 115°C for an industrial grade device, the
2
ispClock5500 Family Data Sheet
# Active Output Banks
4
(b)
6
OUT
=100 MHz)
8
10
(4)