ir3508z International Rectifier Corp., ir3508z Datasheet - Page 15

• Manufacturer Part Number: ir3508z
• Description: Xphase3 Phase Ic
• Manufacturer: International Rectifier Corp.

LAYOUT GUIDELINES
The following layout guidelines are recommended to reduce the parasitic inductance and resistance of the PCB
layout; therefore, minimizing the noise coupled to the IC.
• Dedicate at least one middle layer for a ground plane, which is then split into signal ground plane (LGND) and
• Separate analog bus (EAIN, DACIN, and IOUT) from digital bus (CLKIN, PSI, PHSIN, and PHSOUT) to reduce
• Connect PGND to LGND pins of each phase IC to the ground tab, which is tied to LGND and PGND planes
• Place current sense resistors and capacitors (R
• Place the decoupling capacitors C
• Place the phase IC as close as possible to the MOSFETs to reduce the parasitic resistance and inductance of
• Place the input ceramic capacitors close to the drain of top MOSFET and the source of bottom MOSFET. Use
• There are two switching power loops. One loop includes the input capacitors, top MOSFET, inductor, output
power ground plane (PGND).
the noise coupling.
respectively through vias.
inductor current sense wires, but separate the two wires by ground polygon. The wire from the inductor
terminal to CSIN- should not cross over the fast transition nodes, i.e., switching nodes, gate drive outputs, and
bootstrap nodes.
respectively.
the gate drive paths.
combination of different packages of ceramic capacitors.
capacitors and the load; another loop consists of bottom MOSFET, inductor, output capacitors and the load.
Route the switching power paths using wide and short traces or polygons; use multiple vias for connections
between layers.
Page 15 of 19
To Bottom
To Digital Bus
To Gate
Voltage
MOSFET
Drive
PLANE
PLANE
PGND
PGND
VCC
PHSOUT
CLKIN
GATEL
NC
PGND
To Switching
and C
Node
VCCL
CS
as close as possible to VCC and VCCL pins of the phase IC
and C
MOSFET
To Top
CS
) close to phase IC. Use Kelvin connection for the
NC
EAIN
CSIN -
CSIN+
VCC
To LGND
To Analog Bus
Plane
To Inductor Sense
Ground
Ground
Polygon
Polygon
Jan 09, 2009
IR3508Z
PLANE
PLANE
LGND
LGND
To VIN