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Issues related to the output and storage of the LTC3588-1 chip

FormerMember
FormerMember

When the circuit is not connected to the supercapacitor, the output is normal. After the circuit is connected to the supercapacitor (5V 0.33f), the output of the circuit becomes weak after one minute, and then there is no output. I would like to ask what is the reason for this? The same is true when I plug in small capacitors or electrolytic capacitors. Is it circuit connection problem or capacitance selection error? My supercapacitor is connected to the Vin port and connected to the ground.

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  • Hello,

    What do you mean by "the output of the circuit becomes weak"?

    Perhaps the leakage of the supercapacitor is slowly pulling energy out of the system until the regulation eventually collapses. It is not uncommon for supercapacitors to have high leakage upon being charged. After being held at a full charge for some time, this leakage will slowly diminish to a much lower DC value.

    Regards,

    Zack

  • hi

    Thanks for your reply, my circuit connection is as shown below. PZ1 and PZ2 are connected to both ends of the piezoelectric transducer. My supercapacitor C4 (5V 0.33f) is connected to the marked position in the figure. I plan to use supercapacitors to store energy, but when the supercapacitor is not connected, the voltage output of the Vout terminal is normal. After the supercapacitor is connected, the output voltage Vout is as shown by the yellow line below. After about 1 minute, the output voltage Vout is 0. 

    Looking forward to your reply

    Liu

  • Hi Liu,

    Does your VIN voltage never exceed the 5V max of the supercapacitor?

    This is an energy-in-vs-energy-out problem. Is there any load on VOUT? What are you powering? Try removing that and see how it impacts the "alive time".

    Also, bear in mind that there is a little power consumption from the IC, some internal leakage from the supercap, and even some from the scope probe for the measurement. All of this will eventually drain the cap on VIN, causing the output to drop out of regulation. It would be good to see what VIN is doing on another channel.

    Regards,

    Zack

  • Hi Zack

    The output of the above circuit is not connected to any load. The output waveform is as shown above. After one minute, there is no output. The LTC3588 chip is broken. Can you help me answer this question?

    thanks

    Liu

  • Hi Liu,

    When you say the chip is broken, do you mean you have to replace it to get an output again? Or if you stop and re-apply the input will it start up again?

    Can you send a waveform of VIN as well as VOUT?

    What current does your piezo device generate? You should not input more than 50mA, and if you are above the shunt voltage (~20V) then you should not exceed 25mA.

    Regards,

    Zack

  • Hi Zack

    The output of the chip is normal before the supercapacitor is connected. When the supercapacitor is connected, the chip is damaged.When the chip is broken, I have to replace it to get an output again, if I stop and reapply the input,it can't start up again.
    Therefore, I think there is no problem with the input of the piezoelectric device. The problem is the supercapacitor, but I can't find the specific reason.

    Liu

  • Hi Liu,

    Sounds like you may have current inrush into the supercapacitor which is blowing the internal rectifier bridge by momentarily violating the 50mA abs max. You may want to try putting current-limiting resistors between your source and the IC to prevent this.

    Alternatively, it may help to put your supercapacitor on VOUT instead of VIN.

    Regards,

    Zack

Reply
  • Hi Liu,

    Sounds like you may have current inrush into the supercapacitor which is blowing the internal rectifier bridge by momentarily violating the 50mA abs max. You may want to try putting current-limiting resistors between your source and the IC to prevent this.

    Alternatively, it may help to put your supercapacitor on VOUT instead of VIN.

    Regards,

    Zack

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