Document Number: 74292

S-61214–Rev. A, 17-Jul-06

www.vishay.com

9

Vishay Siliconix

SiP41111

Thermal Consideration

The thermal issue of the IC cannot be ignored because the

driver IC is the power conversion device. The IC can gener-

ate unexpected amount of heat to have high temperature if

the thermal issue is not carefully considered at begin of the

system level design. The additional heat sink for the IC will

increase the cost of materials. The best solution to settle the

thermal issue to improve the reliability of the system design

is to increase the trace copper area as much as possible for

heat dissipation. The PCB traces are not only for electrical

connection. It is also used for heat dissipation

.

The PowerPAK SOIC package is designed to meet the

higher ambient environment operation. A heat dissipation

pad is built under the body of the SOIC package. Availability

of heat dissipation pad under the body of the package

doesn't means the thermal issue can be ignored because the

PowerPAK is designed to mount the body of the package on

the PCB trace for heat dissipation. The PowerPAK cannot

dissipate enough heat to provide a cool environment for the

IC because the surface area of PowerPAK is small. Large

trace area is the best way to control the temperature of the

IC in the high ambient environment.

Layout Consideration

Careful PCB layout design is absolutely necessary for any

high frequency switching device to avoid circuit function and

EMI issues. The following guideline should be carefully fol-

lowed to optimize the performance of SiP41111 driver.

decoupling ceramic capacitor right next to the IC from

MOSFET should be as small as possible. It is strongly

recommended to place the IC right next to the gate of the

MOSFET to form small driving loop between pin HO, HS,

LO and Vss because high frequency, huge instanta-

neous current is being sunk and sourced in these loop to

drive the gate of the MOSFET, which look like a large

capacitive load to the device. If the physical distance can

not be minimized due to PCB layout mechanical specifi-

cation, the width of the loop traces should be increased

as much as possible to reduce the impedance of the loop

traces.

Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon Tech-

nology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and reliability