CSD87384M

SLPS415D – SEPTEMBER 2013 – REVISED MARCH 2015

www.ti.com

6 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI ’ s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

6.1 Application Information

The CSD87384M NexFET™ power block is an optimized design for synchronous buck applications using 5 V

gate drive. The Control FET and Sync FET silicon are parametrically tuned to yield the lowest power loss and

highest system efficiency. As a result, a new rating method is needed which is tailored toward a more systems-

centric environment. System level performance curves such as Power Loss, Safe Operating Area, and

normalized graphs allow engineers to predict the product performance in the actual application.

6.2 Power Loss Curves

To simplify the design process for engineers, TI has provided measured power loss performance curves.

Figure 1 plots the power loss of the CSD87384M as a function of load current. This curve is measured by

configuring and running the CSD87384M as it would be in the final application (see Figure 27). The measured

power loss is the CSD87384M loss and consists of both input conversion loss and gate drive loss. Equation 1 is

used to generate the power loss curve.

(1)

The power loss curve in Figure 1 is measured at the maximum recommended junction temperatures of 125°C

under isothermal test conditions.

6.3 Safe Operating Curves (SOA)

The SOA curves in the CSD87384M data sheet provide guidance on the temperature boundaries within an

operating system by incorporating the thermal resistance and system power loss. Figure 3 to Figure 4 outline the

temperature and airflow conditions required for a given load current. The area under the curve dictates the safe

operating area. All the curves are based on measurements made on a PCB design with dimensions of 4 inches

(W) × 3.5 inches (L) × 0.062 inch (T) and 6 copper layers of 1 oz. copper thickness.

6.4 Normalized Curves

The normalized curves in the CSD87384M data sheet provide guidance on the Power Loss and SOA

adjustments based on their application-specific needs. These curves show how the power loss and SOA

boundaries adjust for a given set of systems conditions. The primary y-axis is the normalized change in power

loss and the secondary y-axis is the change in system temperature required to comply with the SOA curve. The

change in power loss is a multiplier for the Power Loss curve and the change in temperature is subtracted from

the SOA curve.

10

Submit Documentation Feedback

Copyright © 2013–2015, Texas Instruments Incorporated