Drive a resistive heater from a low power IC

I'd like to drive a resistive heater using an IC operating at 3.3 V. The heater may need to dissipate up to 18 W, and will be powered by a 28.8 V battery. The IC is able to generate PWM signals, but driving the heater should be as little noisy as possible. Finally, the driver shouldn't dissipate too much energy.

To prevent switching the high current flowing through the resistor, and thus EM noise emission, I thought about putting a simple RC low-pass filter before the actual driver, which would smooth its input signal.

Now, for the driver itself, using a MOSFET would be easy, however they dissipate more power than bipolar transistors, so a Darlington pair might be more appropriate. Then, the issue of the high base-emitter voltage arises, since the PWM signal will have a 3.3 V amplitude.

What is the appropriate way to do this?

• FETs don’t “dissipate more power than bipolars” that statement is either blatantly false, or at the very least circuit dependent and requires more qualification. Feb 23, 2019 at 15:22
• @EdgarBrown The resistive nature of MOSFETs leads to power losses quadratic with the current, while the fixed voltage drop of BJTs leads to linear power dissipation. Then, FETs dissipate more power than bipolars, at least asymptotically. Are the constants involved the key, or I am being wrong elsewhere ? Feb 23, 2019 at 15:49
• “quadratic with the current” is only an issue if the quadratic curve is above the linear one, and then it’s only an issue for the static losses not the dynamic ones. A MOSFET with a 5mOhm Rds_on requires 40A to equal the static losses of a bipolar and, as dissipation is quadratic, would have 1/2 the dissipation at 20A. And this is for ideal bipolars. If your statement was true CMOS technology would not be the dominant one, precisely due to power dissipation. Feb 23, 2019 at 15:56
• What does "as little noisy as possible" mean? Where (what circuit node) are you concerned about having noise in? How much noise is acceptable ("as little as possible" is not a useful spec)? What frequency bands of noise cause problems? What frequencies is your PWM source able to operate at? Feb 23, 2019 at 15:56
• Suppose heat required is less than about 100 C. A RC filter ahead of a MOSfet driver results in the MOSfet(s) dissipating heat - can you mount the MOSfet(s) driver as part of the assembly that delivers heat? You can likely use a RC time constant that only filters the gates rise & fall edges of PWM from your microcontroller - how much determines the heat delivered by the MOSfet(s). Feb 23, 2019 at 16:43