IRDC3651
Rev 1.1
12/20/2006
RD-0616
3
CIRCUIT LAYOUT - TOP LAYER
The PCB is a 4-layer FR4 board. The IR3651 IC
and the associated passive components are
mounted on the top side of the board.
Solder pads for off-board connections to various
power supply options and control signals are
placed on the top layer.
Off-board connections to ground are available on
the bottom layer.
Figure 2 – Top layer of the IR3651 evaluation board.
Power supply decoupling capacitors, the charge
pump capacitor and feedback components are
located close to the IR3651 IC. The feedback
resistors are connected to the output voltage at
the point of regulation and are located close to
the IC.
Either R9 or R10 (default) must be
installed to implement the required single
point of connection between Signal
Ground and Power Ground.
Two different MOSFET configurations can be
used: eight-pin SOIC packages on the top side
of the board or MX-packaged DirectFets on the
bottom side of the board. The bottom–side
location of the DirectFet packages allows
convenient mounting of heat sinking devices
The input and output energy storage
capacitors and the power inductor are placed
close to the MOSFET packages.
To improve efficiency, the circuit board is
designed to minimize the length of the on-
board power ground current path.
Two alternatives are provided for implementation
of the required single point of connection
between Signal Ground and Power ground.
Install a zero ohm resistor at location R10 to
implement the shortest available connection
between the grounds. Installation of R10 is the
minimum–noise solution and is the default. If
R10 is removed and R9 is installed, an
approximation of remote voltage sensing is
available. Remote sensing will minimize voltage
error due to ground currents, but may be more
vulnerable to high-frequency noise.
