LT8410-1 Booster Circuit Current Draw

Hi,

I'd like to get some support regarding Linear's LT8410-1 boost converter. 

More specifically I am measuring a large disrepancy between simulated current consumption (using LTspice) and the reality of my circuit. 

To be more precise the boost converter is set to convert about 3.4V to 13.25V or 26.5V. I am measuring about 150uA current drawn from my supply in the first case and about 3mA in the second case. LTspice simulates an average current draw of ~130uA in the first case and about 250uA in the second case. 

The situation is a bit more complicated but I would like to discuss this in private if possible with one of the support engineers.

Thank you for any support.

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  • Hello Dulcevida,

    Thank you for your reply. 

    I have run the simulation and can confirm what you are saying but.....what started all this is in your very last sentence. 

    'That yields a duty cycle of <1%, for a very low average current from the battery.'

    When I run the simulation I am measuring the average current out of the source V1. This in the case of 50V output with 3.4V input is in the order of 200uA and generally agrees with bench measurements. 

    In the case of 100V output the simulation shows an average current of about 420uA coming out of the source. 

    Although the switch current may peak at 3 and 8mA respectively as you mention, the average source current is much much smaller than this. 

    The question then arises is the average source current that we should be looking at or the rms? The rms is shown as indeed much higher in the simulation and closer to the actual bench measurement (about 3.5mA both in simulation and bench.) However the rms when the output is 50V is simulating as 1.2mA which is way higher than in the bench measurement. 

    Also all of the above are with 4uA load at 105V output and 2uA load at 53V (due to load resistor). 

    When the load is removed, the average current out of the source drops to 300uA (in simulation) which is CONSISTENT with the datasheet value shown for quiescent current in regulation with no load for the part:

    At 34.5V output the current is shown as about 300uA.

    So my opinion is that there is still something wrong with my circuit that causes excessive current draw from the supply at 100V. 

    It would be great if you could help me more on this. 

    Thank you.

Reply
  • Hello Dulcevida,

    Thank you for your reply. 

    I have run the simulation and can confirm what you are saying but.....what started all this is in your very last sentence. 

    'That yields a duty cycle of <1%, for a very low average current from the battery.'

    When I run the simulation I am measuring the average current out of the source V1. This in the case of 50V output with 3.4V input is in the order of 200uA and generally agrees with bench measurements. 

    In the case of 100V output the simulation shows an average current of about 420uA coming out of the source. 

    Although the switch current may peak at 3 and 8mA respectively as you mention, the average source current is much much smaller than this. 

    The question then arises is the average source current that we should be looking at or the rms? The rms is shown as indeed much higher in the simulation and closer to the actual bench measurement (about 3.5mA both in simulation and bench.) However the rms when the output is 50V is simulating as 1.2mA which is way higher than in the bench measurement. 

    Also all of the above are with 4uA load at 105V output and 2uA load at 53V (due to load resistor). 

    When the load is removed, the average current out of the source drops to 300uA (in simulation) which is CONSISTENT with the datasheet value shown for quiescent current in regulation with no load for the part:

    At 34.5V output the current is shown as about 300uA.

    So my opinion is that there is still something wrong with my circuit that causes excessive current draw from the supply at 100V. 

    It would be great if you could help me more on this. 

    Thank you.

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