Im trying to understand the datasheet of these components to see if they are compatible. but im not sure i understand the terminology correctly.
I want to use the VOM1271 opto-coupler as an isolated driver for the IRF7010 MOSFET with arduino.
This is what i understand, and please correct me if im wrong:
- It sais that the VOM1271 has an “open circuit voltage” of 8.4 volts. does that mean that it could provide 8.4 volts to the mosfet gate? or what does open circuit voltage accually mean?
It means the output voltage is 8.4V with no load, when the input is active. With just a MOSFET connected
that will be the voltage too, since MOSFET gates are only capacitive.
- the “short circuit current” is 15uA. so that would be the current that the opto can supply on the output?
Yes, so if you were to be foolish enough to connect a resistor between MOSFET gate and source you’d likely
stop the device working completely. It also means the turn-on will be slow as the gate capacitance will
be charged with only 15µA, rather than 100+mA a conventional driver chip would supply. You
therefore cannot use this device with PWM.
- The VOM1271 LED forward voltage rating is min: 1.2, max 1.6. i assume its the voltage i should supply from the controller. so i would have to use a dropping resistor?
Yes, its an LED inside.
- The IRF7010 mosfet seams to be fully saturated with the 8.4v Gate-to-Source Voltage according to the datasheet graph?
10V nominal, but 8.4V should work. I don’t know why PV opto’s aren’t rated for >= 10V, as that’s
standard for many MOSFETs. You could simply use a logic-level MOSFET to guarantee full drive.
- As i understand MOSFETs are voltage driven. so even at the very low 15uA it would turn on?
the O in MOS means oxide. The gate is isolated using silicon dioxide (amorphous quartz), its not
electrically connected and takes no current (well, perhaps a few nano-amps). The electric field
is what controls the conducting channel by electrostatic induction. Hence the FE in FET stands
If all my assumtions are correct it should be possible to run the ciruits below, right?
Yup its designed for SSR use (but not with PWM as I mentioned).