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synchronous buck converter

synchronous buck converter

synchronous buck converter

(OP)
I am trying to develop a circuit to convert 5-18Vdc, 100ma max to 0.4Vdc, 400ma.  I am working on a synchronous buck converter design but I am finding limited resources on a discrete design.  All of the buck converter IC's I found do not go low enough and have inadequate efficiency when they are even close.  I have been toying with the idea of using the basic synchronous converter with a P and N channel fet.  The problem is that I am trying to use a MSP430 microcontroller to drive the circuit.  What would you reccomend for a gate driver for the upper P-channel fet?  If you any other suggestions please put them in too.
Thanks

RE: synchronous buck converter

Hi, I'd be inclined to split the converter into 2. Use an off the shelf unit to get down to 3v, then have you discrete converter to go down to 0.4.

RE: synchronous buck converter

A synchronous converter can be tricky with a microcontroller, as the timing between the MOSFETs has to be tight to avoid overshoots or a good efficiency.

RE: synchronous buck converter

(OP)
cbarn24050,
I like that idea, I'll have to look at that one.  Efficiency is of great concern so I will have to see if that will work.

felixc,
I haven't seen a problem yet with "shoot through" or efficiency.  I have the PWM code already written and put in a delay between switching each seperate gate drive.

The problem I am dealing with the most is that the microcontroller I am using is a 3V logic high and I can't drive the gates with that, especially the P-channel FET.

Thanks for the input so far.

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