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# Power Dissipation for MOSFET CSD17303Q5

Other Parts Discussed in Thread: CSD86350Q5D

We are using the part CSD86350Q5D in our design. Under section Absolute Maximum Rating(Page2 of Datasheet) Power Dissipation is mentioned as 13W. Under section Power Block Performance parameter Power Loss is mentioned as Typ2.8W. In our design Vin = 12v, Vout = 1.05v. Iout= 20A

Now for doing thermal simulation what is the value we need to consider for power dissipation. Is it 2.8W

• The value of 13W in the abs max table is a thermal limit. It only implies that this is the maximum amount of power the device can handle without burning out.

Actual power loss will be much closer to 2.8W.

If you look at Figure 1 on the datasheet, actual power loss at 20A looks to be around 2.5W. Using your specific operating conditions, you can then modify this number by multiplying it by the appropriate normalized values as shown in the design example section of the datasheet. Since Vin for you is 12, the normalized loss due to Vin will be 1. Since Vout is 1.05, Figure 8 tells us the normalized power loss will be around .95. You can determine similar numbers for your specific switching frequency and output inductance using figures 6 and 9 respectively and from there get a pretty good estimate of how far the actual power loss will deviate from 2.5W.

Let me know if there is anything else I can assist you in.

Is it that for Vin = 12v, Vout = 1.05v, Iout=25mA, L = 0.47uH

Power dissipation = power loss for 20A output current * Normalized power loss for vout of 1.05v * Normalixed pwr loss for inductance of 0.47uH * Normalized power loss for switching frequency

Basically we need to multiply all these factors. Is my understanding correct?

Also here switching frequency means what? Where do we need to look for this parameter?

Regards

Sudha

• Yes Sudha, your understanding is correct.

Switching frequency is the frequency you are driving the power block at. It is a choice determined by your design and the limitations of the power block and driver IC that you will be using this device in conjunction with.