LT1302 Boost converter, efficiency issue

I am using the LT1302CN8-5#PBF, boost converter.

I have built exactly same circuit as the first page of the following datasheet document is presenting. https://www.analog.com/media/en/technical-documentation/data-sheets/lt1302.pdf

Components I used:

  • 100uF cap : ESL107M050AGMAA
  • 10uH Inductor : RLB0608-100KL 
  • Diode : 1N5819
  • 0.1uF cap: Ceramic disc capacitor. Unknown part number.
  • 0.01uF cap: Ceramic disc capacitor. Unknown part number.
  • 20K ohm resistor : Unknown part number.

My input voltage is 3.7V and max input current is 5A. 

When testing with DC electronic load, the boost converter circuit output voltage starts to drop below 5V when current output is only 125mA.

My target output current is 300mA, but then the voltage output will drop below 3V

The testing result is very far from what I read from the datasheet document and the LtSpice simulation. What could be the issue?

Thank you for your help.

  • +1
    •  Analog Employees 
    on Nov 7, 2019 10:44 AM

    Hello,

    The chosen inductor (550mA?!) is way too small, according to the datasheet the inductor should be capable of 2.5-3A without saturation.You can check the peak currents in your circuit with the LTSpice schematic you mentioned.

    Although the LT1302 is pretty old, it operates at a high switching frequency of 400kHz. Hence the layout is important for final performance. Page 11 in the ds shows more details on this. How does your circuit look like in real life?

    And if possible, you should change to a modern and better part, like the LT8494 which offers similar current and input voltage range.