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TPS61040 3.3V -> 12V Circuit

Matthew Krenik
Intellectual 675 points
Other Parts Discussed in Thread: TPS61040

Hello,

I'm using the TPS61040 chip.Specifically, the 3.3V to 12V reference circuit that is in Figure 20. I'm using the recommended inductor and diode, as well as the same values for the capacitors. Resistor values are slightly different. I've implemented this on a custom board.  

Unfortunately, I'm getting some strange waveforms, and some ripples/spikes on the input (3.3V) power line as well as the output (12V) power line. These waveforms were collected with a load of 300 ohms. I've attached these waveforms below. 

Any idea what might be going on? How can I reduce these spikes and ripples on both the input and the output? 

Switching voltage

Input

Output

  • 0
    TI__Intellectual 2270 points

    Hi Matthew,

    Maybe the ground of ur scope is not so clean, the cope ground should not be the power ground. You can try some ground blade or ground spring to reduce the spike.

     

    Charles

  • 0
    TI__Intellectual 1305 points

    Hi Matthew,

    The input output spike is mainly due to the switching noise.

    Please check your PCB layout. Make sure that is input and output capacitor is as close as to the IC and SW pin trace is as short as possible.

    BTW, add a small cap (maybe 1uF or smaller) at the output, very close to the IC, it may help to reduce large noise at the output.

    BR

    Gene