Any one seen or used these?

[shortbus=]

I'm being told that using this chip, FDA215 (data sheet attached) allows a mosfet high side switch to be made with no boot strapping needed. It flies in the face of all I know(which I admit isn't much) about high side mosfet switches. They are claiming that you just use them to drive the gate and no boot caps or diodes are necessary, just connect the input to the led to your signal, and the output to the gate and source of your mosfet.

Anyone? Help?

 

[fourtytwo]

Its a LED driving a tiny PV array that generates enough voltage to turn on a fet, only problem is it takes up to 5mS to do it so not much use for smps or similar applications. I have only ever looked at these style of devices but never used one, ok for a static switch I guess.

 

[gophert]

The are ok in an H-Bridge that doesn't have to change direction rapidly. The high side is switched on and the low side is then pulsed at any frequency that makes you happy.

 

[shortbus=]

Its a LED driving a tiny PV array that generates enough voltage to turn on a fet,

I understand that part. But from what I know/understand a high side mosfet needs the gate voltage to be source voltage plus turn on voltage. The circuit it was in was 12V on the D-S and 12V to the gate at turn on. Wouldn't that mean in a normal half bridge driver the boot strap cap would need to supply the extra 12V to keep it turned on? Or am I wrong about that?

If that understanding is correct, How does just getting the original 12V gate voltage from the FD215 continue to keep the mosfet on? And I forgot to mention the signal to turn on the gate through the FDA215 is the only gate connection.

I guess old age is setting in.

 

[sagor1]

I've seen those PV types of triggers, but for low side only (N-MOSFET). I have not seem any for high side (P channel)

 

[rjenkinsgb]

It creates a switchable, floating, power source that you connect directly between source and gate on the device you want to control.
As it is floating, the absolute source voltage does not matter.

The FET type makes no difference, as long as the polarity is correct for the gate relative to the source.

Most of the applications examples show them used to make simple solid-state relays, but there is no reason they cannot be used for any other gate drive application where the low switching speed does not matter.

 

[shortbus=]

Most of the applications examples show them used to make simple solid-state relays, but there is no reason they cannot be used for any other gate drive application where the low switching speed does not matter.

Then why aren't they being used more or similar parts being made by more companies? Even for PWM motor drives they would simplify the switching, just use them for the high side, keeping them on , and switch the low side for PWM. No longer a need for a half bridge driver, which is the most common way of doing it.

 

[KeepItSimpleStupid]

They appear to be really cool.

I haven't heard about them until now. I THINK a lot of the high power MOSFETS require a much higher gate voltage/
At low power levels, I can't think of any reverseable applications except toys and drills.

I haven't read much about the design of dynamic or regenerative braking H-bridge designs.

 

[shortbus=]

Well I did some more looking today for information on them. It seems they first were brought out in 2005, or at least that's the date on the App. Note, and it was International Rectifier that developed the idea.

To answer what KISS said about higher voltages and currents, the one I first asked about and all of them can be connected in either series or in parallel to get what is needed. There is Also another of these, FDA217 that can take up to 10V in and give 12V out put. There is another series of these from Infineon PVI15033 https://www.mouser.com/api/CatalogN...neon-PVI5033R-DataSheet-v01_00-EN-1733015.pdf

Here is the App. Note, AN 1017 Shows the many ways these can be used.

 

[Visitor]

Hmmm. Interesting possibilities to power an isolated circuit.

 

[KeepItSimpleStupid]

Here https://www.vishay.com/docs/49261/49261_pt0313.pdf (VOM1271) is one that's considerably faster.

 

[shortbus=]

Hmmm. Interesting possibilities to power an isolated circuit.

did you notice in the app note how they can be used as a galvanically isolated DC power supply, with no transformer?