DC-DC Boost Circuit 200mv to 3V LTC3105

Hi everyone,

I intend to use DC-DC boost circuit to archieve 3V output with 0.2~0.5V input by applying LTC3105. But when I measured the output voltage, I just receive 1.31V. Does anyone tell me what wrong is in my circuit. I appreciate for all of recommendations and suggestions.

If May misunderstand your diagram, but Vin is your input and LDO is a linear output less than Vout.

So you are using it backwards.

Ok, I see. That is just the markers, Dc-out is the V-in in my circuit and I use the voltagage at LDO for voltage supply to sensing circuit.
When I measure the output of LDO and V_out, I have the same value 1.3V. Could you tell me how to fix it?

Generally one debugs a design by scoping each component to verify each performs as it should and there are no unexpected losses.

YOu must learn how to current probe with 50 mV shunt R's using differential probe method with very short ground connections or coax to shunt using A-B mode.

Verify L performance for DCR, C performance for ESR and leakage, then track layout capacitance on critical feedback then input and outputs on each pin of the IC.

Verify your load is what you expect etc. and LDO load is not excessive!
Then consider if you have damaged part from ESD improper handling if all else passes.

Fix your schematic to show properly all inputs and outputs with layout photo after you have checked the above and report findings.

Make sure your "sensing cct" does not pull up current rather it sinks current as LDO's only source and not sink current.