ir2110 output resistance

[vered&alon]

hi all,

I have a circuit using the ir2110 and two transistors (fb180a10p) as it's switches.

We want to calculate the time constant RC of them (the output resistance of the driver and the input capacity of the transistors) and compare it to the switching friquency.

My problem is that I don't know the output resistance of the driver.

I know it got something to do with the tempreture, but I don't know how...

PLEASE HELP!!!

the ir2110 datasheet is attached

 

[WimRFP]

hello,

I checked the data sheet also (it doesn't mention it).

You can make some guess. The functional diagram shows mosfets in the ouput and a minimum sink/source current of 2A (at 15V supply).

So the maximum output resistance in this case would be 15/2=7.5 Ohms. In practice, the situation is more complicated. When the mosfet (inside the chip) starts discharging the gate capacitance, it will probably operate more like a current source, when the voltage at the drain (of the mosfet inside the chip), drops sufficiently, it will behave like a resistor (saturated mosfet).

When you are fine with 7.5 Ohms, in reality the discharge and charge of your mosfet gate (fb180a10p) will be faster because of the current source behavior of the output of the chip.

Just assuming the output of the chip is a current source may give a somewhat too optimistic switching time (based on the total gata charge of your mosfet).

If it really matters, best is to measure it with a varying resistive load (under pulsed conditions).

Look to page 13 to know the sink/source current in case of other supply voltage.

 

[vered&alon]

thanks wimrfp, that was the kind of help we needed