Thermal Information for DVHF2805S/DVHF2800D/DVHF2800T
The DVHF DC/DC converters utilize hybrid technology. All the power semiconductor
chips such as linear regulator, MOSFET, and Schottky diode are attached to an Alumina
substrate and the substrate is then attached to the metal case which houses the DC/DC
converter. The power transformer however is directly mounted to the metal case through
a thermally conductive epoxy preform. Table 2.1 shows the maximum junction
temperature rise (鈭員
JC
) at full load operation of all the power components referenced to
the outside of the base plate of the metal case. The case-ambient thermal resistance
(胃
CA
)of the metal case between the base plate of the metal case and ambient is also listed
in the table.
A simplified and conservative way to calculate the worse case junction temperature of all
the power components is as follows:
1) Measure the worse case input power (Pi) and output power (Po) of the DC/DC
converter according to the system requirement and calculate the total power
dissipation (Pd) equal to Pi-Po.
2) If no additional heatsink is attached to the converter, the case temperature of the base
plate of the metal case (T
C
) is equal to Pd*胃
CA
+ T
A
where T
A
is the ambient
temperature and the value of
胃
CA
comes from the table. If any additional heatsink is
attached to the converter, the new effective
胃
CA
needs to be used.
3) The worse case junction temperature (T
J
) of all the power components is then equal to
Tc +
鈭員
JC
where the value of
鈭員
JC
is from Table 2.1.
The maximum junction temperature of all the power components are rated at 175
擄
C.
Additional heatsink is always recommended in order to maintain a low junction
temperature of the power components so that a higher reliability number can be achieved.
Table 2.1 Thermal Data for DVHF DC/DC Converters
鈭員
JC
of Linear Regulator
鈭員
JC
of MOSFET
鈭員
JC
of Schottky Diode
鈭員
JC
of Power Transformer
胃
CA
, Case to Ambient Thermal Resistance
12
擄
C
7
擄
C
9
擄
C
12
擄
C
25
擄
C/W
1
