I need a simple gate driver IC for a PMOS Switch (Asynchronous Buck Converter)

[Quank]

Hi,
I'm doing an High Current Buck Converter for charging a Battery very fast. I have designed the Buck Conveter with a 20 A PMOS Switch. The Battery charger uses a Battery controller with a PWM output but with very low current limitations. The aplication chart gives a gate driver circuit based in several BJT's but I can't understant it and it is not pefectly suitable with my application. Does anybody know any IC for driving the PMOS switch with a 2 A peak?
Thank you

Quank

 

[Sceadwian]

2 amps or 20 amps? We can't understand any circuit you can't provide a schematic for... The driving circuitry required will depend on the specific Mosfet you're talking about.

 

[Quank]

20 a

2 amps or 20 amps? We can't understand any circuit you can't provide a schematic for... The driving circuitry required will depend on the specific Mosfet you're talking about.

Thank you for answer. I attach the schematic of the Buck Converter. The P-MOSFET is the Vishay Siliconix SUP75P03-07-E3. I attach the specifications too. I need to work with high current because I want to charge a Li-On 40 AH Battery in 4 hour more or less.
The MOSFET has a total Qg of 160 nC. If I want a fast swiching of aprox tr 50 ns I need at last 2 A for driving the MOSFET. The controller BQ2954 has a PWM output that only gives 10 mA.
The specifications of BQ2954 gives a example circuit for driving a transistor using two NPN, one inductance and one diode, but I'm not sure to understand it and I think is a little dificult to tune. Is there any easier solution, like an IC?
Thank you in advance

Quank

 

[Sceadwian]

Why do you want 50NS switching? That's equivalent to 20Mhz! I can't see any rational for switching so abruptly or at that frequency for a battery charger. Also you should be able to charge a Lithium pack in 1 hour, 2 tops if you peak charge and balance the whole pack. What cell layout are you using that's giving you such a high amp/hours, that's gotta be a BIG battery.

 

[ronv]

What is your input voltage to the charger? You could probably use just a simple FET driver for the FET.

 

[peufeu]

Try a FAN3111E MOSFET Driver

 

[Quank]

Sceadwian:
I'm sorry, I think I don't explained it very well. I mean than I want a swiching on delay, ie, time to change from the OFF state to the ON state (no the global period) of aprox 50 ns with a frequency of 100 KHz. I want also a swiching off dealy, ie, time to change from the ON state to the OFF state of aprox 50 ns. The battery size is aprox half of a car's battery.
Thank you for your answer.

ronv:
The output voltage is 4.25 V. I'm looking a FET driver, in fact. Thanks.

peufeu:
The driver you give me is very good, but it is well suited for a NMOS FET. I aprecciate this driver, and I think I will use it. Thank you for the answer.

In conclusion:
I've been looking a lot, and I think that is better to change the PMOS for an NMOS. I though that it would be better to use a PMOS for a simpler driver circuit, but in practice I realized that there's a lot of drivers for NMOS swichs and I have more options. I also have more cheaper swichs with NMOS and it is not so dificult to change the swich.

Thank you everbody.
I give the problem solved.

 

[ronv]

You will need a PFET for the high side switch. So 4.5 out how much is the input voltage to the FET.

 

[Quank]

ronv: I don't need a PFET for the high side. It is possible to put a high side switch NMOS. The input voltage to the FET is 12 V.
Thanks. I think I know what I must do.

 

[ronv]

Don't forget the gate needs to be 10 volts above the source to properly turn on the NFET.

 

[peufeu]

There's a mistake on the schematic you posted, look at BQ2954 page 5, the "-" side of the battery and the "-" side of the capacitor are connected to the wrong point on your schematic.

Do a DigiKey search on category MOSFET Drivers, Hi-Side, you can probably do it with an NMOS.

 

[ronv]

Ahh. I see the dilemma. You want to switch 20 Amps continuous at 100Khz to keep the inductor small. You may have to bite the $bullet and use a larger inductor and a lower frequency to avoid the switching losses. But yes the NMOS will be faster for the same current.

 

[peufeu]

Some high side drivers :

LM5112
FAN7371

you need to check that they can start into a pre-biased load... what is your battery voltage ?