International Rectifier IR3651 User Manual
USER GUIDE FOR IR3651 EVALUATION BOARD
DESCRIPTION
IRDC3651
The IR3651 is a high voltage PWM
controller designed for high performance
synchronous Buck DC/DC applications . The
IR3651 drives a pair of external NMOSFETS using a programmable switching
frequency up to 400kHz allows flexibility to
tune the operation of the IC to meet system
level requirements, and synchronization
allows the simplification of system level filter
design. The output voltage can be precise ly
regulated using the internal 1.25V re ference
voltage for low voltage applications.
Protection functions such as under voltage
lockout and hiccup current limit are pro vided
to give required system level security in the
event of fault conditions.
CONNECTIONS
J2: VIN= 48V
This user guide contains the schematic and
bill of materials for the IR3651 evaluation
board. The guide describes operation and use
of the evaluation board itself. Detailed
application information for the IR3651
integrated circuit is available in the IR3651
data sheet.
Evaluation Board Specifications:
VIN= 48V, tolerance 10%
V
= 3.3V at 10A
OUT
FS= 100kHz
Rev 1.1
12/20/2006
OUT
= 3.3V
J3: V
J4, J7: GROUND
J5: Shutdown control input
J6: Sync input
J1: External 12V supply option.
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CONNECTION DIAGRAM
IRDC3651
48V
Power
Supply
Load:
3.3V@
0A to 10A
Note: Ground connection pads are located on
the bottom side of the circuit board.
Figure 1 – Connections to IR3651 evaluation board
for default configuration .
Rev 1.1
12/20/2006
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IRDC3651
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.
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.
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 volt age
error due to ground currents, but may be more
vulnerable to high-frequency noise.
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 onboard power ground current path.
Either R9 or R10 (default) must be
installed to implement the required single
point of connection between Signal
Ground and Power Ground.
Figure 2 – Top layer of the IR3651 evaluation board.
Rev 1.1
12/20/2006
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CIRCUIT LAYOUT- BOTTOM LAYER
Solder pads for off-board connections ground are
available on the bottom layer. A portion of the
bottom layer plane is isolated for use as Signal
Ground. Options for making the required single
point of connection between Signal ground and
Power Ground are provided on the top side of the
board.
MX-packaged DirectFets can be mounted on the
bottom side of the board. The bottom–side location
of the DirectFet packages allows convenient
attachment of a heat sink.
Low Voltage
Linear Regulator
Components
IRDC3651
The IR3651 controller requires a low voltage
power source (nominally 12V). Elements of a
simple linear voltage regulator are installed on
a circuit pattern provided on the bottom layer to
generate the required voltage from the 48V
input supply.
Alternatively, a separate external 12V supply
can be connected at J12, on the top side of the
board.
Off - board Ground
Connection Pads
DirectFet
Positions
Heat Sink mounting area (optional)
Figure 3 – Bottom layer of the IR3651 evaluation board.
Rev 1.1
12/20/2006
RD-0616
Signal Ground
Plane
4
LAYOUT -- MID-LAYERS
The two mid-layers are used primarily for Power
Ground.
IRDC3651
Mid-layer 1 Mid-layer 2
Figure 3 – Internal layers of IR3651 evaluation board.
Rev 1.1
12/20/2006
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