LTC3105 & LTC3108 for thermoelectric generator

Hello.

I want to boot output voltage of thermoelectric generator (TEG).

I had successfully used LTC3108 for voltage booster using low impedance peliter TEG.

But the LTC3108 didn't work well, when I connected high impedance TEG.

I saw some article LTC3105 is for high impeance TEG, and LTC3108 is for low impedance.

I bought the LTC3105 and connected all of passive chips (inductors, capacitors, resistors), but the chips and circuit didn't work.

If I use all of same chips in LTC3105 datasheet typical applications for TEG and apply input voltage about 250mV using power supply with series of 200ohm resistor, is it will work well?

I want to know that the circuits work well using power supply before connecting TEG.

How to confirm? and How to start-up the chips?

  • 0
    •  Analog Employees 
    on May 21, 2019 3:48 PM

    Hi, 

    Which TEG are you using for the design? TEG spec dominantly helps in selecting the correct part and configuring the application circuit accordingly. What is the output requirement?

    If you are using LTC3105 for the design, MPPC pin voltage should be set as per the output voltage of the TEG.

    If you want to confirm the circuit before connecting to the TEG you can check for Vout , LDO and AUX voltages by connecting the circuit to any power supply for required input voltage. Vout should regulate to the configured value. Figure 1 on Page 9 of the datasheet gives the startup sequence of the converter. First AUX and then LDO needs to be charged up before Vout to start up. Once AUX is higher than 1.4V it starts charging LDO. Once the LDO reaches it regulation point AUX starts charging Vout. So the input capacitance should be selected such that it should be able to charge up both AUX and LDO during the startup. Usually input capacitance of 470uF or higher is recommended for a startup voltage of 0.25V.

    You can also refer our demo-board DC1587A for LTC3105 for your design. The circuit should work well if you configure pins correctly as per the design requirements.

    Thanks   

  • Hi. Thank you for kind explanation.

    My TEG has high impedance about 200ohm, and it can generate voltage from 300mV to 1000mV

    I want to boost the voltage for 2.4V as typical application in dataseet. In typical application in datasheet,
    I confirmed 30 kohm resistor was used.

    You said MPPC pin voltage should be set as per the output voltage of the TEG,
    then how to apply it for my TEG and how to configurate MPPC part? 

    You also said the iuput capacitance of 470uF or higher is recommended for start-up,
    but capacitance of 100uF was used in typical applications in datasheet.
    Could you recommend input capacitance and inductance (10uH in datasheet) for my device?

    Thanks.

  • 0
    •  Analog Employees 
    on May 24, 2019 6:58 PM in reply to HCho953

    Hi, 

    470uF capacitance is recommended when startup voltage is 0.25V. The application in datasheet has a TEG with mppc set voltage of 0.3V so input capacitance of 100uF works well. 

    If the TEG generated voltage is 0.3V to 1V the application in datasheet should work well. Mppc voltage can be set to 0.3V. 

    Thanks