CSD97370AQ5M

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SLPS352A – SEPTEMBER 2011 – REVISED MAY 2012

APPLICATION INFORMATION

The Power Stage CSD97370AQ5M is a highly optimized design for synchronous buck applications using

NexFET devices with a 5V 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 rating method is used that is tailored towards

a more systems centric environment. The high-performance gate driver IC integrated in the package helps

minimize the parasitics and results in extremely fast switching of the power MOSFETs. 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.

Power Loss Curves

generated by the devices. In an effort to simplify the design process for engineers, Texas Instruments has

provided measured power loss performance curves. Figure 7 plots the power loss of the CSD97370AQ5M as a

function of load current. This curve is measured by configuring and running the CSD97370AQ5M as it would be

in the final application (see Figure 18). The measured power loss is the CSD97370AQ5M device power loss

which 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 7 is measured at the maximum recommended junction temperature of

Safe Operating Curves (SOA)

The SOA curves in the CSD97370AQ5M datasheet give engineers guidance on the temperature boundaries

within an operating system by incorporating the thermal resistance and system power loss. Figure 9, Figure 10,

and Figure 11 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 4.0" (W) x 3.5" (L) x 0.062" (T) and 6 copper layers of 1 oz. copper thickness.

Normalized Curves

The normalized curves in the CSD97370AQ5M data sheet give engineers guidance on the Power Loss and SOA

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

boundaries will 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 is system temperature required in order 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.

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