choosing power sully switcher

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My question is about how i choose my voltage regulator for fpga after i know what my current and voltages .

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What is the external voltage that you will creating the power supplies from?

Typically you would use a switch-mode power-supply (SMPS) for conversion of the input supply (say 12V) to a lower voltage, eg., 3.3V for I/O, or say 1.0V for a core voltage. For lower current rails, linear regulators can be used.

For each FPGA, Altera typically has a power supply design guideline. Look on the page where you can download the handbook. At the top of the page are links to the pin outs and configuration guidelines.

Cheers,

Dave

Hey.

I have a 3.3 V in that i will convert,so basically what is better switcher or Ldo?

What parameters are critical for my power converter to obtain?

Thx.

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I have a 3.3 V in that i will convert,so basically what is better switcher or Ldo?

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Convert to what?

If you want to convert to 12V, then you need a switcher (boost) converter.

If you want to convert to 2.5V, then you can use a linear regulator, or a switcher. You determine which one to select based on current.

For example, conversion of 3.3V to 2.5V using a linear regulator involves a voltage drop of 3.3V - 2.5V = 0.8V over the linear regulator. The linear regulator will dissipate P = VI = 0.8V * I, where I is your load current. If your circuit needs 1A, then you will dissipate P = 0.8W. If you look in the linear regulator data sheet, it will tell you the thermal resistance of the package for a given PCB layout. Lets say its 60-degrees C per W. This means that at 25C room temperature, your linear regulator die temperature will be T = 25C + 0.8 W * 60C/W = 73C. You then need to check what the maximum die temperature allowed by the linear regulator is. If its 75C, then you do not have much margin in your system.

As a typical rule of thumb, if your load current is under 500mA, just use a linear regulator, if its above 1A, use a switcher, and if its between 500mA and 1A, use either, depending on what the circuit is, and your preferences.

Cheers,

Dave