LTC3113
16
3113f
it is incumbent upon the user to verify proper operation
over the intended system’s line, load and environmental
operating conditions.
The junction-to-air (θ
JA
) and junction-to-case (θ
JC
) thermal
resistance given in the “Pin Confi guration” diagram may
also be used to estimate the LTC3113 internal temperature.
These thermal coeffi cients are determined using a 4-layer
PCB. Bear in mind that the actual thermal resistance of
the LTC3113 to the printed circuit board depends upon
the design of the circuit board.
The die temperature of the LTC3113 must be lower than
the maximum rating of 125°C, so care should be taken in
the layout of the circuit board to ensure good heat sinking
of the LTC3113. The bulk of the heat fl ow is through the
bottom exposed pad of the part into the printed circuit board.
Consequently, a poor printed circuit board design can cause
excessive heating, resulting in impaired performance or
reliability. Refer to the PCB Layout Considerations section
for printed circuit board design suggestions.
As described in the Thermal Shutdown section, the
LTC3113 is equipped with a thermal shutdown circuit that
will inhibit power switching at high junction temperatures.
The activation threshold of this function, however, is
above the 125°C rating to avoid interfering with normal
operation. Thus, it follows that prolonged or repetitive
operation under a condition in which the thermal shutdown
activates necessarily means that the die is subjected to
temperatures above the 125°C rating for prolonged or
repetitive intervals, which may damage or impair the
reliability of the device.
Figure 3c. Top Layer of Example PCB Figure 3d. Bottom Layer of Example PCB
THERMAL AND
PGND VIAS
APPLICATIONS INFORMATION
