That's 'gate enhancement' above the 5v'. Meaning with a 5v supply, the gate will get 12v. See figure 11.
Ohhh, I see. I misunderstood, I thought it was an absolute value.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
Still, it's probably best not to add more load to my 5V regulator when I could be running the gate driver from the 12V supply.
Note that there are 2 different ICs, a mic5014 and a mic5015. The bootstrap circuit you are showing us is using the mic5015.
Huh, must be a typo; figure 3's little illustrated waveform on the input pin shows 'on' as high state, which corresponds to the 5014. The only difference between the 5014 and 5015 is that the input pin logic is inverted.
Figure #3 and only figure #3 is bootstrapped to improve turn on speed by externally boosting the V+ instead of relying solely on the IC's internal charge pump. All other circuits use the internal charge pump to generate the +12v above the source voltage reference input pin on the IC.
So, the fig. 3 circuit
is meant to be considered in it's entirety? The wording of the description of it is pretty confusing and made it sound to me like they were talking about two separate things.
I tried simulating the bootstrap part, and I think I understand how it works now. The 1uF cap together with the 1N4001 diodes acts as an external 'pump', and the 100nF cap continually stores the boosted voltage. So, this helps because the MIC5014 won't have to do a 'ramp up' with it's own charge pump? And I assume this is what enables higher switching speeds, because the higher gate voltage is always available right from the word go.
Hmm, I don't really need higher switching speed. I'm not PWM-ing or anything. So, this circuit would probably be a waste of time, right? Although, I guess it would mean the power FETs spend less time in the linear region on turn-on, but I don't know whether that's really of any significance with my usage scenario (switching on/off at most maybe once every 2 seconds).
But, if your only concern is powering a 5v mosfet rail, why not just use a logic level p-channel mosfet?
The whole purpose of this IC is so you can drive highside N-channel mosfets up with a 30v rail.
I can't use a P-channel MOSFET. I'm driving one winding of a motor that has a dual windings (two speeds), and when the motor is driven from one winding, it generates a voltage on the other winding that's higher than the supply voltage. P-channel FETs get turned on uncontrollably when that happens, hence the back-to-back N-channel diodes which block it.