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UCC27212: Power loss difference of MOSFET and gate drive IC between 4A/4A driver and 3.5A/2.5A driver

Genius 13540 points
Part Number: UCC27212
Other Parts Discussed in Thread: UCC27284

Hello,

Our customer has some questions about our gate driver ICs.

Due to their board layout issue, they are going to use UCC27212 for their 1st prototype.
Then they will change it to UCC27284 or UCC27272 in the next prototype because they want to decrease VCC down to about 6V.

UCC27212 is a 4A/4A driver while UCC27284/282 are 3.5A/2.5A drivers.
They would like to know how drive current difference affect power loss of MOSFET and gate drive IC iteslf.

Question 1)
They would like to know whether there is difference in the power loss of MOSFET between using UCC27212 and using UCC27284/282.
They use three MOSFETs with QG=73nC(at 6V) and RG=0.6ohm(TYP)/1.1ohm(MAX) in parallel for both low side and high side.
The external gate drive resistance is 1 ohm that is shared for all 3 MOSFETS.

Question 2)
They also would like to whether there is difference in the power loss of gate driver IC itself between UCC27212 and UCC27284/282.

Regards,
Oba

  • Hello Oba,

    Thank you for supporting the UCC27212 and UCC27284 with your customer. The difference in MOSFET losses based on gate driver current is based on a number of factors including the dynamic parasitic capacitances of the MOSFET which affects the Vds rise and fall times as well as the peak current in the power train etc.

    The UCC27284 is actually fairly conservatively rated so the performance will likely be better than the datasheet typical 2.5/3.5A suggests. To estimate Vgs rise and fall times just based on datasheet typical currents: dt=dQ/I for 4A dt will be 54ns for 219nC total Qg. For 2.5A dt is 87ns rise time and for 3.5A dt is 62ns fall time.

    The total gate drive loss for both drivers will be the same and is Pgd= VDD x Qg total x fsw. So this is dependent on the switching frequency, VDD and total Qg of both HO and LO connected Mosfets. There is a difference in the amount of the gate drive power dissipated in the IC. This is determined by the gate driver internal resistance and external gate resistance which splits the gate drive power.

    The gate drive power dissipated in the IC is determined by Pd= Pgd x Rgd/(Rgd + Rgate + Rgfet) where the Rgd is the average of the pullup and pulldown resistance in the gate driver, Rgate is the external gate resistance and Rgfet is the MOSFET internal gate resistance. The UCC27284 has a pullup resistance of 1.3 Ohms and pulldown of 0.85 Ohms for an average of 1.08 Ohms. The UCC27212 has a pullup resistance of 2.3 Ohms and pulldown resistance of 1.3 Ohms for an average resistance of 1.8 Ohms. So the UCC27212 will dissipate a higher percentage of the total gate drive power. But the total gate drive power is the same.

    Confirm if this addresses your question, or you can post additional questions on this thread.

    Regards,