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Question asked by ramalho.jose on Nov 2, 2016

We are finishing the design of a solar light using the SPV1040.


Reading the datasheets, application notes and testing the evaluation board STEVAL-ISV006V2, we had a general vision regarding circuit performance.


Anyway there is two critical questions that we didn’t find an answer in documentation.


Question 1


We designed all circuit following AN3319 and in page 14 chapter 6 the topic ‘Input Voltage Partitioning’ suggest a resistor from Vmpp-set to PV+ with 1 K ohm (R3 in circuit of page 12).


Why use a low value like 1 Kohm that will sink to much current from solar panel ?


Can we use at least 10K in such resistor ?


What current needs Vmpp-set pin to operate correctly ?



Question 2


Is same topic is not detailed what the relation between solar panel Vmp and the voltage in Vmpp-pin.


Is mentioned that to SPV1040 start operation needs >=0.3V in Vmpp-set pin.


That is the voltage in the Vmpp-set pin when the solar panel reach the Vmp voltage ?


In another words we should start SPV1040 at solar panel Vmp or at a lower voltage ?


If we should start SPV1040 at a lower voltage, than Solar Panel Vmp, what the relation between Solar panel Vmp and SPV1040 start voltage.


To be more clear, if the solar panel have a 2.5V Vmp voltage, we should calculate the both resistors in Vmpp-set pin to have >= 0.3V when solar panel reach 2.5V or before that ?



An answer to the above questions will be helpful to set-up the final values and finish the design.


Thanks in advance.