PWM

Driver

Driver

Switch

Node

Load

Control

FET

Sync

FET

Input

Supply

11

CSD87355Q5D

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SLPS575 – MARCH 2016

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Application Information (continued)

The CSD87355Q5D is part of TI’s Power Block product family which is a highly optimized product for use in a

synchronous buck topology requiring high current, high efficiency, and high frequency. It incorporates TI’s latest

generation silicon which has been optimized for switching performance, as well as minimizing losses associated

eliminating parasitic elements between the Control FET and Sync FET connections (see Figure 28). A key

challenge solved by TI’s patented packaging technology is the system level impact of Common Source

Inductance (CSI). CSI greatly impedes the switching characteristics of any MOSFET which in turn increases

switching losses and reduces system efficiency. As a result, the effects of CSI need to be considered during the

MOSFET selection process. In addition, standard MOSFET switching loss equations used to predict system

efficiency need to be modified in order to account for the effects of CSI. Further details behind the effects of CSI

and modification of switching loss equations are outlined in TI’s Application Note SLPA009.

Figure 28.

The combination of TI’s latest generation silicon and optimized packaging technology has created a

CSD87355Q5D versus industry standard MOSFET chipsets commonly used in this type of application. This

comparison purely focuses on the efficiency and generated loss of the power semiconductors only. The

performance of CSD87355Q5D clearly highlights the importance of considering the Effective AC On-Impedance

technology.