Hello,
I have been tasked with designing a 0-24V, 2.5A (max) output power supply that will be controlled from my 3.3V microcontroller via a DAC. It needs to be fairly precise and they want to be able to dial in very low voltages (they would like ~2mV control accuracy as it is a 16-bit DAC). I anticipate having to source the supply from my 24V rail. Other then the 24 & 3.3V rail, I only have a low current +/-12V rail that is sourcing some other circuitry. With these given conditions, I'm looking at trying to design a SEPIC converter using a PWM controller rather then direct DC/DC (avoiding the low voltage limit). Because of the voltage levels I'm having some trouble selecting a part to start the design with.
Currently I am looking at trying to design using TPS4300. If I understand the data sheet correctly these are the issues:
1) Due to high output voltage, I need to use gate drivers between NDRV and PDRV and their MOSFETs
2) Again due to to the higher voltage, I will need to have a voltage divider before bringing the voltage back to the VOUT and an additional divider before returning to the FB pin.
3) Due to wanting the digital control, I would need that FB pin to be driven by a summing amp mixing the output of a DAC with the voltage shifted feedback.
So my questions are:
1) Am I approaching this correctly?
2) Is there a simpler way to achieve the goal?
3) What am I overlooking?
Thank you for any assistance!
Best regards,
Ron