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problem with LM5000

Jamall Davis
Prodigy 20 points
Other Parts Discussed in Thread: LM5000

I'm currently trying to input 3.7  into the LM5000 and get out a voltage of 11.5. The problem I'm having is it actually knocks the voltage down to 3.2 V. I believe i followed the data sheet correctly and given the appropriate components for the buck booster function.

The above picture is a pcb design of my LM5000. The lower left is the input for my battery, with the red as Vcc and the blue GND. The very top has my my capacitors at parallel and the two resistors in the formation to promote the the voltage gain. The rest of the components are the many resistors and capacitors the datasheet ask for. 

  • 0
    TI__Guru* 76745 points

    From your description, the LM5000 did not look like ever switched in your circuit, and the 3.2V output is most probably the passthrough voltage of your 3.7V input, and the 0.5V different is the diode drop of the rectifie. 

    It is not clear how you followed the datasheet. In the section of layout that you showed, Pin 4 is not connected to anything.  And, the layout need to be greatly improved:  power traces width, ground planes, etc.  Please contact TI local FAEs in your region for more support.