# Doubts in using UCC27537 Gate driver to drive IPA60R120P7XKSA1 MOSFET

I want to use UCC27537 gate driver to drive IPA60R120P7XKSA1 MOSFET but I have some doubts.

1. To avoid voltage oscillations at the gate, do I need to include resistors in between MOSFET and gate-driver?
2. According to the datasheet, the gate driver can source up to 2.5A and sink 5A, so is it the current when no resistor is connected between the MOSFET and the gate-driver or we have to limit it to the given current?
3. in the datasheet of MOSFET, it is given that the MOSFET gate resistance is around 8 ohms, so should I connect external resistors?
4. If the resistor is required then a lot of power will be lost through this resistor, is there any special resistor for this? or recommend me any if you have any idea...

To avoid voltage oscillations at the gate, do I need to include resistors in between MOSFET and gate-driver?

The purpose of the resistor is to share power and to reduce overshoot (A side effect of ringing). This resistor value may not be necessary or it might be crucial. Your best bet is to just try different resistor values and see what works best. Often times a 0 Ohm resistor works just fine.

According to the datasheet, the gate driver can source up to 2.5A and sink 5A, so is it the current when no resistor is connected between the MOSFET and the gate-driver or we have to limit it to the given current?

The gate driver is essentially a current source. It will provide that much current at whatever voltage it can.

The actual current at any time is found through analysis of the circuit. The circuit shown here is a simplified version of what is happening. It will give you a good idea of what the current is. In this example the instant the gate driver voltage goes high the current in the circuit will be 1.5A. Then the current will decay as the capacitor charges up. simulate this circuit – Schematic created using CircuitLab

in the datasheet of MOSFET, it is given that the MOSFET gate resistance is around 8 ohms, so should I connect external resistors?

Test the circuit. This largely depends on the physical layout of the circuit. Long traces add inductance and can lead to overshoot. So, if you see overshoot or ringing add a resistor.

If the resistor is required then a lot of power will be lost through this resistor, is there any special resistor for this? or recommend me any if you have any idea...

A resistor is a resistor it dissipates power. (P = I^2R) Reducing resistance without increasing current will result in less power dissipated.

• In your last line, you appear to be saying that charging a capacitor via a lower value resistor results in less dissipation. Are you aware that this might be a fallacy? Jan 7, 2021 at 15:07
• I am aware now of what I have implied. I will fix what is there. Jan 7, 2021 at 16:43

If you cannot simulate the conditions well with parasitic well, you will not be able to get a hint if an external resistor is needed or not! Therefore if you don't have that possibility It's wise to include a resistor for elaboration of suitable drive strength through all operating conditions.

Considering you have a driver that provides both OUTH and OUTL, it would be even wise to have a resistor on both sides, just for that. Generally, the UCC2753x data sheet on page 27 tells you about the use of gate resistors: - I think this explains why you might want to use a gate resistor (mainly to share power dissipation between the chip and an external resistor). Look at the above formula; it is telling you this: -

• $$\0.5\cdot Q_g \cdot V_{DD}\$$ is the energy taken to charge up the gate capacitance of the MOSFET
• Multiply that by frequency ($$\F_{SW}\$$) to get the power dissipation for each toggle
• If you factor in a value for $$\R_{GATE}\$$ you get less power burnt inside the chip
• $$\R_{OFF}\$$ and $$\R_{ON}\$$ are the driven resistances of the driver chip (lowside and highside)

If you are driving a single MOSFET then I doubt that a gate resistor is important however, many applications will require one in order to reduce the dissipation inside the driver chip.