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LTM4653 as a variable output voltage power supply


I’m currently designing a variable output voltage buck convert for driving a baffle heater (my company works on EGSE for space instruments).

I need to generate a variable voltage between ~5V to ~50V for closing thermal loops on resistive elements (25 Ohm minimum resistance).

My idea is to use the LTM4653 buck module which have good specification on paper (good Vin and Vout window).

To control the output voltage I was thinking about two solutions:

  • Using a 5V DAC along with a current mirror that would drain the output current from the Iset pin by removing it from the resistor that sets the output voltage. So when the DAC out is max (5V) the output voltage is minimum and vice versa.
  • Connect 5V DAC directly to Iset pin (through buffer) and connect the Vosns pin not directly to Vout (as I see in all circuit implementation of LTM4653) but at a midpoit of a 1/10 voltage divider.

Would you recommend this kind of approach and this component for this application? Do you have any suggestion? Has anyone tried to use the component in this way?

For now LTSpice simulation shown quite good results. I think the tricky thing is finding the right switching frequency to get the best compromise between ripple and efficiency across the entire output voltage range. Its also importat to mantain good stabilty margin aswell.

Many thanks and happy new year to all of you.

Francesco - Saitec s.r.l.