TIDA-010042: TIDA-010042 MOSFETS for 40A

Amar,

I think we may have a MOSFET option from TI that may not mean changing the PCB too much.

We have lower resistance MOSFETs like the 100V CSD19532Q5B or 80V CSD19502Q5B that I think could do the job. They will run quite hot and you will need to adjust the switching frequency down to say 50kHz, then also adjust the inductor to about 30uH to get acceptable ripple current. I am not sure if there is such high inductance high current available on the market, you will need to check.

The CSD19502Q5B and the CSD19532Q5B should both fit on the same PCB footprint as the design.

I ran some calculations of losses using this tool, as this is a 2 phase design I used the tool assuming 20A per phase:

http://www.ti.com/tool/fetpwrcalc

I came up with around 2.5-3Watts of losses @ 50kHz, this is about as much as this package can handle in a typical application, see article here for reference:

How to choose the right power MOSFET or power block package for your application

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Other Parts Discussed in Post: CSD17581Q5A When starting a new design, engineers are often overwhelmed by the number of package options for power metal-oxide semiconductor field-effect transistors ( MOSFET s) and power blocks . For example, TI offers...

I have added the STP75NF75 mosfets to the PCB design. Please let me know if there is any issue with using these before I order the board. I am planning to add a heat sink.

Thanks

Amar,

I think it best you pursue this information from the manufacturer of the MOSFET, in this case ST Microelectronics.

Ok I will, thank you for your help.

Regards,

Amar,

I am assuming you are referring to TIDA-010042, this is dictated by Vcc applied to Vdd pin of the driver. In the schematic it shows 10V Vcc applied to the Vdd pin. So the gate drive on the MOSFET gate will be 10V.

Absolute max rating for each MOSFET if the Vgs spec in the datasheet. For the case of the ST FETs and the TI FETs I suggested the max allowed Vgs voltage is 10V

Amar,

I mad an error in my previous statement and said max allowed for the TI and ST MOSFETs was 10V, this is incorrect, I should have said 20V. So a 10V gate drive if fine for any of them.

Amar,

These MOSFETs are used like load switches, so Power Loss can be calculated using I2R , you can then use the attached blog to get an idea of what power loss per package you could typically be able to dissipate.

In your case the CSD18540Q5B on the board in the original reference design would dissipate @ 20A ~1W (20*20*Resistance @ temp), however 40A would dissipate closer to 5W most likely. Which is normally too much for a SON5x6 package on the pcb.

You will need to find a FET that can handle the current of 40A or double the amount of CSD18540Q5B to split the current between them.

How to choose the right power MOSFET or power block package for your application

TI E2E support forums

Other Parts Discussed in Post: CSD17581Q5A When starting a new design, engineers are often overwhelmed by the number of package options for power metal-oxide semiconductor field-effect transistors ( MOSFET s) and power blocks . For example, TI offers...