IRDC3898 International Rectifier, IRDC3898 Datasheet - Page 16

• Manufacturer Part Number: IRDC3898
• Description: Power Management IC Development Tools Design Kit POL IC
• Manufacturer: International Rectifier
• Type: DC/DC Converters, Regulators & Controllersr

Specifications of IRDC3898

• Product: Evaluation Boards
• Tool Is For Evaluation Of: IR3898
• Input Voltage: 12 V
• Output Voltage: 1.2 V
• Factory Pack Quantity: 1

12) Layout Considerations
The layout is very important when designing high
frequency switching converters. Layout will affect
noise pickup and can cause a good design to
perform with less than expected results.
Make the connections for the power components in
the top layer with wide, copper filled areas or
polygons. In general, it is desirable to make proper
use of power planes and polygons for power
distribution and heat dissipation.
The inductor, output capacitors and the IR3898
should be as close to each other as possible. This
helps to reduce the EMI radiated by the power
traces due to the high switching currents through
them. Place the input capacitor directly at the PVin
pin of IR3898.
The feedback part of the system should be kept
away from the inductor and other noise sources.
The critical bypass components such as capacitors
for Vin, Vcc and Vref should be close to their
respective pins. It is important to place the
3/17/2011
Compensation parts
should be placed as
close as possible to
the Comp
Resistor Rt and Vref
decoupling cap should
be placed as close as
possible to their pins.
pin.
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3898.
Based on the results of the continuing evaluation, this board can evolve and change without notice
IRDC3898 Demo board layout considerations – Top Layer
AGnd
Vin
Confidential
PGnd
AGnd
feedback components including feedback resistors
and compensation components close to Fb and
Comp pins.
In a multilayer PCB use one layer as a power
ground plane and have a control circuit ground
(analog
referenced. The goal is to localize the high current
path to a separate loop that does not interfere with
the more sensitive analog control function. These
two grounds must be connected together on the
PC board layout at a single point. It is
recommended to place all the compensation parts
over the analog ground plane in top layer.
The Power QFN is a thermally enhanced package.
Based on thermal performance it is recommended
to use at least a 4-layers PCB. To effectively
remove heat from the device the exposed pad
should be connected to the ground plane using
vias. Figure 43 illustrates the implementation of the
layout
IRDC3899 4 layer demoboard.
AGnd
Vin
Vin
guidelines
ground),
IRDC3898-Vtt rail
Vout
to
outlined
which
PGnd
Vout
Enough copper &
minimum length
ground path between
Input and Output
above,
All bypass caps
should be placed as
close as possible to
their connecting pins.
PGnd
SW node copper is
only kept at the top
layer to minimize the
switching noise.
all
signals
on
Vout
16
are
the