Electronic – selectable power voltage

fpgai2cldomicrocontrollervoltage-regulator

I want to build a circuit that will output multiple voltages (one at a time) to supply an FPGA. The core volt will be constant voltage. I want to be able to supply different voltages for the FPGA output and input pins. Virtex4,5,6 and 7 all can support 1.2v, 1.5, 1.8, 2.5 to name a few. I would like to have a MCU or another FPGA select different output voltages with SPI, I2C or GPIO. I was looking for a TI regulator module that supported I2C or SPI and found none. I also was thinking of using a LM317 adj regulator ( open to your input) and switching in and out resistors. I could switch the resistors in and out with a FET controlled by GPIO with a decoder.

I know it can be done, because I used a board in College that did just that. It was controlled through a FPGA and usb software. I did not have a schematic of this board and the vendor who sold it wouldn't give me any info.

I want to be able to supply the above voltages with 1A, 2A, 4A and 10Amp – depends on the FPGA used.

Best Answer

You could use a digital potentiometer in the feedback path of a voltage regulator.

From Analog Devices MT-091:

Because they are digitally controlled, digital pots can be used in active control applications, in addition to basic trimming or calibration applications. For example, digital pots can be used in programmable power supplies as shown in Figure 8A. Typical adjustable low dropout voltage regulators (such as the anyCAP series) have a FB pin, where applying a resistor divider yields a variable output voltage. As shown, R1 and R2 are the feedback and input resistors, respectively. The FB circuit has an internal non-inverting amplifier which gains up a 1.2-V bandgap reference to the desired output voltage.
digital pot

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