There is a diagram on page 7 of the LTC3106 (Datasheet) named "Start-up into resistive load" and i couldn't find any explanation on the internet how to understand it.

My assumption is: This diagram shows what load is allowed at the output of the ltc3106 for a given Vin at start-up without getting any problems. So this means: if i have 100Ohms load, the ltc might get problems at start-up with 3V Vin.

Is this right?

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    \$\begingroup\$ I would imagine it means what you say. \$\endgroup\$ – Andy aka Jul 28 '17 at 11:27

Your assumption is correct. This chart describes the minimum resistance, using a 10uH Inductor, that will allow the converter to startup. Otherwise it will not start or go into a protection mode.

Many microcontroller and system on a chip semiconductor loads are not resistive in nature and only start to draw significant current after they reach a certain voltage and go through a startup sequence. If your load is a microcontroller or processor then you can adjust this startup time to allow the converter to start.

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  • \$\begingroup\$ Indeed, with 10uH and 100mA load at least 4.5V are required. I tested 30uH and now 4.1V is ok. Any links/literature how to calculate the inductor value that is needed for about 3.5V startup? Testing different values seems not to be the best option \$\endgroup\$ – S.G Jul 30 '17 at 11:30
  • \$\begingroup\$ As you have found, the larger inductor will reduce the peak and value ripple current of the boost/buck converter allowing you to adjust the values shown in the table a little. However, I would not think it would change much from your experiments and I would not recommend for high volume applications. Which application diagram fits your use the best? \$\endgroup\$ – Surfncircuits Jul 31 '17 at 22:26
  • \$\begingroup\$ Sry, but I don't understand your answer. Can you explain it once again? \$\endgroup\$ – S.G Aug 1 '17 at 18:50

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