Hi everybody
This is a very great thread! I also have similar questions with mengghee, and I find lots of answers in here. I want to make sure, if I am to drive unipolar 5Vdc(rating) / 0.4A(max) DC motor with IRF540 (the one available in campus), is the attached circuit and the Rg calculation below can be done?. The input signal is from either directly from microcontroller ATmega (max 40mA) or even Optocoupler (Imax=100mA).
Based from VVV and Kral's asnwers, determining Rg is;
1. deltaVgs = deltaId/Gfs(datasheet) = 0.4A/20 = 0.02V.
So Vgs = Vgs(max,datasheet)+deltaVgs*temp_compensation = 4V+0.02V*1.2 = 4.024V
2. Rds_on = 0.077Ohm for 10V.
At T=100degC, Rds_on = 0.077Ohm*1.6 (datasheet, curve) = 0.1232 Ohm
3. Switching time = tsw = 45ns (datasheet).
Because Vgs = 4.024V, Q = around 5nC (datasheet, curve)
Because the signal voltage = 5V, then voltage accross Rg = VRg = 5-4.024V = 0.976V
Ig = Q/tsw = 5nc/45ns = 1/9A.
So Rg = 0.976V/(1/9A) = 9.784Ohm
My questions:
1. Is this circuit and Rg applicable? Is there any other theoretical/practical consideration that I need to put into account?
2. I think the signal current (Ig=1/9A) will be too big to be handled by microcontroller (max 40mA) or even Optocoupler (AQW211, Imax=100mA), or is it?. Is there any way to reduce the Ig without reducing the performance?
Thank you for any help you can provide.
- MOSFET IRF540 datasheet:
https://www.google.com/url?sa=t&sou...4JmPBA&usg=AFQjCNHWB1nHU__wqYgcz3-XNUeV4yQ-ZQ
- Motor datasheet (see T2-03 e-Compact):
https://www.parker.com/portal/site/... - ULTRA-COMPACT DIAPHRAGM PUMP&vgnextfmt=EN#