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TPS61202: Load regulation above max value when driving audio

Nick Nick
Prodigy 80 points
Part Number: TPS61202
Other Parts Discussed in Thread: LM4853,

Hello, I am using a TPS61202 to supply 5V to an audio circuit (utilizing the LM4853). I'm following the reference schematic in the TPS61202 datasheet: 2.2uH inductor with 2A saturation current, 22uF input and output capacitors, 25V, X5R. Input voltage is anywhere between 2V and 4V, the issue remains no matter the input voltage (tried both bench power supply and lipo battery). I'm measuring voltage right at the output of the converter.

What I see on the scope, when the volume is turned up (not too high, only 100s of mW at most), I can see the audio waveform imposed on the 5V rail. If loud enough, the ripple voltage can reach past 100mV peak to peak. The TPS61202 datasheet indicates a Load Regulation of 0.5% max, which would be 25mV, correct?

Is this not the correct specification I should be looking at? I didn't expect low frequency ripple voltage to be an issue on the converter. What can be done to decrease this ripple?

  • 0
    TI__Expert 8245 points

    May be the load is too light then the frequency may be lower. Can I ask what is the load current?

  • 0 in reply to Nini Zhong
    Prodigy 80 points

    So I just took some rough measurements, the load current during the loudest audio portion is only approximately 30mA to 50mA out of the 5V supply. The rest of the system draws roughly 600mW, or about 120mA from the 5V supply. But, if I turn the audio off, the ripple disappears. It's maybe 30mV peak to peak without the audio on. But, when the volume is maxed out, the 5V supply ripple very clearly follows the same waveform, in the kHz frequencies, sometimes past 100mV peak to peak!

  • 0 in reply to Nick Nick
    TI__Expert 8245 points

    I don't think it's the problem of the boost device. The noise is sourced from the audio. May =be because of the bad SW node layout/