InnoSwitch3-EP
Recommendations for Circuit Board Layout
+
See Figure 16 for a recommended circuit board layout for an
InnoSwitch3-EP based power supply.
R1
Rꢅ
1ꢆꢃ1ꢃ8
Single-Point Grounding
Use a single-point ground connection from the input filter capacitor to
the area of copper connected to the SOURCE pins.
Bypass Capacitors
ꢀ
S
ꢁ
The PRIMARY BYPASS and SECONDARY BYPASS pin capacitor must
be located directly adjacent to the PRIMARY BYPASS-SOURCE and
SECONDARY BYPASS-SECONDARY GROUND pins respectively and
connections to these capacitors should be routed with short traces.
ꢁꢂꢃꢄ
ꢅPP
IS
Primary Loop Area
InnoSwitch3-EP
The area of the primary loop that connects the input filter capacitor,
transformer primary and IC should be kept as small as possible.
ꢀꢁꢂ8ꢃ10ꢂ081ꢄ1ꢄ
Primary Clamp Circuit
A clamp is used to limit peak voltage on the DRAIN pin at turn-off.
This can be achieved by using an RCD clamp or a Zener diode
(~200 V) and diode clamp across the primary winding. To reduce
EMI, minimize the loop from the clamp components to the
transformer and IC.
+
R1
Thermal Considerations
Rꢅ
The SOURCE pin is internally connected to the IC lead frame and
provides the main path to remove heat from the device. Therefore
the SOURCE pin should be connected to a copper area underneath
the IC to act not only as a single point ground, but also as a heat
sink. As this area is connected to the quiet source node, it can be
maximized for good heat sinking without compromising EMI
performance. Similarly for the output SR MOSFET, maximize the PCB
area connected to the pins on the package through which heat is
dissipated from the SR MOSFET.
ꢀ
S
ꢁ
ꢆ.ꢅ ꢇ
ꢁꢂꢃꢄ
ꢅPP
IS
InnoSwitch3-EP
ꢀꢁꢂ8ꢃ11ꢂ0ꢄ1818
Sufficient copper area should be provided on the board to keep the
IC temperature safely below the absolute maximum limits. It is
recommended that the copper area provided for the copper plane on
Figure 14. (Top) Line OV Only; (Bottom) Line UV Only.
ꢆR ꢑꢒꢓ
ꢀ
ꢁ
InnoSwitch3-EP
ꢎꢆ
100 ꢉꢑ
ꢁꢂꢃꢄ
ꢀꢌꢔꢕꢋꢌꢍ ꢑꢒꢓ
ꢋꢉꢊ ꢎꢈꢉꢏꢌꢈꢐꢐeꢌ
S
ꢅPP
IS
ꢆeꢇꢈꢉꢊꢋꢌꢍ
ꢎꢈꢉꢏꢌꢈꢐ ꢁꢎ
ꢀꢁꢂ8ꢃ1ꢄꢂ081ꢅ1ꢅ
Figure 15. Fast AC Reset Configuration.
13
Rev. D 08/18
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