e7765 Semtech Corporation, e7765 Datasheet - Page 9

• Manufacturer Part Number: e7765
• Description: 1.3 Ghz Quad Pin Electronics Driver
• Manufacturer: Semtech Corporation

The power consumption goes up as the power supplies
are raised in voltage, and the RADJ, FADJ and DBIAS set-
tings are increased for higher frequency performance.
There are specifications and graphs for the relationships
of these controls to overall performance in the DC Specifi-
cations section. Refer to them for choosing the settings
for a particular system performance. This section deals
with how to heatsink the various power dissipation levels.
Cooling Considerations
Depending on the applied power supply levels and bias
conditions the E7765 will use, various methods of
heatsinking will be required to keep the maximum die junc-
tion termperature within a safe range and below the speci-
fied maximum of 100°C.
The E7765 package has an integral heat slug located at
the top side of the package to efficiently conduct heat away
from the die to the package top. The thermal resistance of
the package to the top is the
specified at 0.8°C/Watt.
In order to calculate what type of heatsinking should be
applied to the E7765, the designer needs to determine
the worst case power dissipation of the device in the appli-
cation. The graph above gives a good visual relationship of
the range of power dissipation that can be expected from
the E7765. The range of power covers the different modes
of operation, power supply settings, and performance bias
adjustments available. Use the data and graphs in subse-
quent sections to determine a particular applications power
dissipation.
Another variable that needs to be determined is the maxi-
mum ambient air temperature that will be surrounding or
blowing on the device and/or the heatsink system in the
application (assuming an air cooled system). A heatsinking
solution should be chosen to be at or below a certain ther-
mal impedance known as R in units of °C/Watt. The
heatsinking system is a combination of factors including
the actual heatsink chosen and the selection of the inter-
face material between the E7765 and the heatsink itself.
This could be thermal grease or thermal epoxy, and they
also have their own thermal impedances. The heatsinking
solution will also depend on the volume of air passing over
Application Information (continued)
©
TEST AND MEASUREMENT PRODUCTS
2006 Semtech Corp. , Rev. 11, 7/18/06
JC
(junction-to-case) and is
the heatsink and at what angle the air is impacting the
heatsink. There are many options available in selecting a
heatsinking system. The formula below shows how to cal-
culate the required maximum thermal impedance for the
entire heatsink system. Once this is known, the designer
can evaluate the options that best fit the system design
and meet the required R .
R (heatsink_system) = (T
where, R (heatsink_system) is the thermal resistance
The graph below uses the power estimates from the previ-
ous graph and indicates the required maximum thermal
impedances required for the heatsinking system using the
above formula with T
Care needs t
Care needs t
Care needs t
Care needs t
Care needs to be tak
DBIAS, RAD
DBIAS, RAD
DBIAS, RAD
DBIAS, RAD
DBIAS, RADJ, F
ture t
ture t
ture to insure adeq
ture t
ture t
im im
im impor
im
.
More information on heatsink system selections can be
read on heatsink vendors’ web sites and in the Semtech
Application Note #ATE-A2 Cooling High Power, High Den-
sity Pin Electronics.
9
por
por
por
portant.
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
o insure adeq
o insure adequat
o insure adeq
o insure adeq
tant.
tant.
tant.
tant.
T
T
P is the maximum expected power
Jmax
ambient
JC
Min Supplies
J, F
J, F
J, F
J, FAD
of the entire heatsink system
(100°C)
expected at the heatsink (°C)
dissipation of the E7765 (Watts)
E7765 junction to case (0.8°C/W)
is the thermal impedance of the
o be tak
o be tak
o be taken when increasing the operating
o be tak
Required Heatsinking Thermal Resistances
AD
AD
is the maximum die temperature
AD
ADJ in
Covers Complete Range of Supplies (All PON=1)
J in
J in
J inputs. Monit
J in
is the maximum ambient air temp
uat
uat
uate heatsinking and air
uat
ambient
puts. Monit
puts. Monit
puts. Monit
puts. Monitoring the die t
en when increasing the operating
en when increasing the operating
en when increasing the operating
en when increasing the operating
e heatsinking and air
e heatsinking and airflo
e heatsinking and air
e heatsinking and air
Jmax
Typ Supplies
at 35°C.
- T
ambient
oring the die t
oring the die t
oring the die t
oring the die tem
- P *
Max Supplies
www.semtech.com
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