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isingla
Level 1
Level 1
First reply posted First question asked Welcome!

I would like to use MOSFET BSC072N04LD and I have two questions about it.

 

  • Which MOSFET controller do you recommend to use with this MOSFET?. The load of the MOSFET will be a RF power MMIC with a supply voltage of 24V and maximum power consumption around 5 A. We will have two MMICs and I think that each one will be supplied with each MOSFET of the two units inside this component.

 

  • I would need to test the time response behaviour of the RF power MMIC. Would it be possible to adquire an evaluation board of the previous MOSFET? In case this MOSFET is not available, could you recommend us an evaluation board of something similar to make these tests?.

 

Thank you very much in advanced for your reply. We would appreciate a quick response.

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1 Solution
Dipti_Kiran
Moderator
Moderator
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250 sign-ins 10 likes received 50 replies posted

Hi @isingla ,

Sorry for delay in response.

Earlier, I did not understand your question correctly.

Here, the circuit in your schematic will not work. Let me explain:

Below figure shows the bootstrap circuit in half bridge configuration. It shows how the bootstrap capacitor charges and discharges (marked with red line). We charge this bootstrap capacitor through the diode when the low side switch is ON. Then this capacitor provides necessary gate voltage for the HS switch to turn ON and this capacitor discharges.

 

Dipti_Kiran_0-1691137625312.png

  Dipti_Kiran_1-1691137625319.png

In your schematic there is no LS switch or any other path to charge the bootstrap capacitor. So, first of all, we must provide the path(ground) to make this capacitor charge. Please be noted, this bootstrap circuit will only work if you are operating the switch dynamically which means continuous turn on and turn off. It will not work in static. Therefore, if you add the path for bootstrap capacitor to charge and you will operate the switch dynamically, then the circuit in your schematic will work.

But if you want to operate your switch in static i.e., if you want your HS switch to be on for a longer duration, then this bootstrap circuit will not work because until then all the capacitor voltage will fully discharge and the HS switch will no longer ON and it will turn off. So, you must use one of the high-side gate drivers with an integrated high-side power supply (charge pump or Boost). One of the suitable gate drivers is AUIR3242STR.

You can connect a load, switch and gate driver AUIR3242STR as shown below. This circuit will always work irrespective of whether you are operating the switch in dynamic or static.

Dipti_Kiran_2-1691137625321.png

 

Regards,

Dipti

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Dipti_Kiran
Moderator
Moderator
Moderator
250 sign-ins 10 likes received 50 replies posted

Hi @isingla ,

RF MMIC is a device which operates at microwave frequency i.e., in the range of 300 MHz to 300 GHz. BSC072N04LD cannot be operated at this high frequency range. You need to choose a device that can operate at this high frequency range. You may choose RF transistor as per your application requirement. Gallium nitride (GaN) is also an option for MMICs as it can also be operated at much higher temperature.

Please go through the link below for RF transistor:

https://www.infineon.com/cms/en/product/rf/rf-transistor/

In order to help you better, could you please tell me your application details in which you are using MMIC device and also please share the circuit diagram(schematic)? What is your switching frequency?

Regards,

Dipti

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isingla
Level 1
Level 1
First reply posted First question asked Welcome!

Dear Dipti,

Thank you for your reply. I think I have not explained correctly my application in my previous post.

I have a 24V voltage available to supply the RF MMIC.

I would use the MOSFET to switch on/off the RF MMIC, removing or applying the 24V supply using a control signal. 
In the attached file, you can see an schematic of what I need to do.

I hope this could help to understand better the application.
Thanks

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Dipti_Kiran
Moderator
Moderator
Moderator
250 sign-ins 10 likes received 50 replies posted

Hi @isingla ,

Sorry for delay in response.

Earlier, I did not understand your question correctly.

Here, the circuit in your schematic will not work. Let me explain:

Below figure shows the bootstrap circuit in half bridge configuration. It shows how the bootstrap capacitor charges and discharges (marked with red line). We charge this bootstrap capacitor through the diode when the low side switch is ON. Then this capacitor provides necessary gate voltage for the HS switch to turn ON and this capacitor discharges.

 

Dipti_Kiran_0-1691137625312.png

  Dipti_Kiran_1-1691137625319.png

In your schematic there is no LS switch or any other path to charge the bootstrap capacitor. So, first of all, we must provide the path(ground) to make this capacitor charge. Please be noted, this bootstrap circuit will only work if you are operating the switch dynamically which means continuous turn on and turn off. It will not work in static. Therefore, if you add the path for bootstrap capacitor to charge and you will operate the switch dynamically, then the circuit in your schematic will work.

But if you want to operate your switch in static i.e., if you want your HS switch to be on for a longer duration, then this bootstrap circuit will not work because until then all the capacitor voltage will fully discharge and the HS switch will no longer ON and it will turn off. So, you must use one of the high-side gate drivers with an integrated high-side power supply (charge pump or Boost). One of the suitable gate drivers is AUIR3242STR.

You can connect a load, switch and gate driver AUIR3242STR as shown below. This circuit will always work irrespective of whether you are operating the switch in dynamic or static.

Dipti_Kiran_2-1691137625321.png

 

Regards,

Dipti

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isingla
Level 1
Level 1
First reply posted First question asked Welcome!

Hi Dipti,

Thank you very much for your reply.

I understand what you say. I have a question about the zener diode between drain and source of the FET. Which is the mission of that diode? How do you configure it?

Thanks.

Best regards,

Ignacio

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Dipti_Kiran
Moderator
Moderator
Moderator
250 sign-ins 10 likes received 50 replies posted

Hi @isingla ,

Zener diode are used “to protect the gate from transients”. It is used for gate source overvoltage clamping. It will clamp the voltage at 18V and will keep the gate source voltage below the maximum Vgs rating i.e., 20V.

Regards,

Dipti

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