ISL78420 Datasheet, PDF (13/16 Pages) Intersil Corporation – 100V, 2A Peak, Half-Bridge Driver with Tri-Level PWM Input and Adjustable Dead-Time

ISL78420
EPAD Design Considerations
The thermal pad of the ISL78420 is electrically isolated. It’s
primary function is to provide heat sinking for the IC. It is
recommended to tie the EPAD to V_SS (GND).
Figure 21 is an example of how to use vias to remove heat from
the IC substrate. Depending on the amount of power dissipated by
the ISL78420, it may be necessary, to connect the EPAD to one or
more ground plane layers. A via array, within the area of the EPAD,
will conduct heat from the EPAD to the ground plane on the bottom
layer. If inner PCB layers are available, it is also be desirable to
connect these additional layers with the plated-through vias.
The number of vias and the size of the GND planes required for
adequate heatsinking is determined by the power dissipated by
the ISL78420, the air flow, and the maximum temperature of the
air around the IC.
It is important that the vias have a low thermal resistance for
efficient heat transfer. Do not use “thermal relief” patterns to
connect the vias.
EPAD GND
PLANE
VDD
LO
EPAD GND
VDD PLANE
HB
HB
VSS
HO
PWM
HS
COMPONENT
NC
LAYER
EN
RDT
This plane is
HB
connected to
HS and is under _HO
all high side
driver circuits
HS
NC
HO
HS
LS
BOTTOM
LAYER
FIGURE 21. RECOMENDED PCB HEATSINK
13
FN8296.1
September 24, 2012