Need help finding IC and datasheet for 4362 DY T25B

[Hi1965]

4362 ic

Need some help finding this pfet which is supposedly being used as a dc converter in a laptop circuit. Have not had any luck finding it or the datasheet. Your help is appreciated.

 

[mister_rf]

finding ic

Maybe it's a SI4362DY

 

[Hi1965]

help finding ic

Thanks a lot. That was the closest thing I could find also. Evidently this mosfet is using 19.8 volts and converting it down to 5.1 volts.Can you tell me why this is being used in combination with an IRF7811A instead of a regular voltage regulator?

 

[mister_rf]

dy 241 transistor

A linear regulator maintains the desired output voltage by dissipating excess power in a power transistor, the SMPS rapidly switches a power transistor between saturation (full on) and cutoff (completely off) with a variable duty cycle whose average is the desired output voltage. The main advantage of this method is greater efficiency because the switching transistor dissipates little power in the saturated state and the off state compared to the semiconducting state for a linear regulator.

 

[Hi1965]

irf 4362

I appreciate your last response and help. It was very timely.I am still trying to understand this circuit and maybe thought you could help.I will explain what I have. Next to the Irf7811A there are two smd capacitors in parallel with continuity from the positive side of the capacitor to the drain of the IRF7811A which is putting out 19.64 voltsdc. The Si4362 mosfets which are also side by side have 0 resistance from the 7811A source to the drain of both 4362 mosfets. Assuming that the 7811 is the controller mosfet and saturation of the gate must be ocurring for voltage to flow from the source to the drain what is its primary function and can you explain how the other 2 mosfets are converting voltage backwards to the gate at 5.1 volts and is there a mathematical formula to compute this? Thanks again.

 

[Sadegh.j]

have you checked alldatasheet.com?

 

[mister_rf]

You have there a synchronous-rectified buck-converter.
The operation of the buck converter is simple, with an inductor and two switches one it's a a transistor and the second a diode, that control the inductor. It alternates between connecting the inductor to source voltage to store energy in the inductor and discharging the inductor into the load. See here more details:

http://en.wikipedia.org/wiki/Buck_converter

A known way to improve the rectification efficiency is to replace the diode rectifier by a synchronous rectifier using an active switch with low conduction loss like MOSFET. A synchronous rectifier has a lower forward voltage drop than a diode due to the much lower drop in a transistor. However, as an active switch a synchronous rectifier needs a driving signal in to turn it on at the appropriate times. In addition, the loss and performance of the active switch is sensitive to the driving signal amplitude and waveform, consequently, the driving method becomes an important issue in synchronous rectifier design.

Some practical examples and the theory involved here:


**broken link removed**
http://www.onsemi.com/pub_link/Collateral/ADP3419-D.PDF
http://www.irf.com/technical-info/whitepaper/syncrecapec2005.pdf
http://www.mnpere.com/Slides_PEBook.pdf
http://www.analog.com/UploadedFiles/Data_Sheets/ADP1828.pdf
http://www.ortodoxism.ro/datasheets2/2/04ksu4x4oyyko6oe2h1ogy455zpy.pdf

 

[Hi1965]

I looked at a lot of the examples but still need some clarification on whats happening. In the case of the notebook; I decided to probe a little further into the voltages on and off. When powered on, the controller mosfet which is the IRF 7811 still had 19.6 volts at the drain but also had 1.5 volts at the source and 1.8 volts at the gate which I assume turns it on. The other 2 SI4362 mosfets had 1.5 volts at the drain and 4.5 volts at the gate when previously there was 5.1 volts at the gate. Does the controller mosfet have some sort of voltage drop across it that somehow 1.5 volts shows up at the source and 1.8 volts arrives at the gate because 19.8 volts is at the drain before power is switched on? I was reading that when the controller is switched on it applies a dv dt to the drain of the other fets. I also gather that the 5 volts at the gate of the switching fets is the gate drive voltage to turn these on, am I correct?However the datasheet for the component says that the gate threshold is 0.6v minimum. Can you elaborate on this in greater detail?