ISL78420 INTERSIL [Intersil Corporation], ISL78420 Datasheet - Page 13

• Manufacturer Part Number: ISL78420
• Description: 100V, 2A Peak, Half-Bridge Driver with Tri-Level PWM Input and Adjustable Dead-Time
• Manufacturer: INTERSIL [Intersil Corporation]

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
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.
VDD
HO
HB
HS
NC
COMPONENT
EPAD GND
LAYER
PLANE
FIGURE 21. RECOMENDED PCB HEATSINK
PWM
RDT
VSS
LO
EN
This plane is
connected to
HS and is under
all high side
driver circuits
13
SS
(GND).
VDD
HB
HO
NC
HS
EPAD GND
BOTTOM
PLANE
LAYER
HB
HO
HS
LS
ISL78420
September 24, 2012
FN8296.1