TPS61099: Converter noise gets into the audio path

Andrew Bogatov

Part Number: TPS61099

Hello!

I use a portable sound amplifier in the device.
The device is powered by a 0.9 - 1.3 V battery
I use a op amp with 2.8V , for this I need a boost converter.

A TPS610993 with 3.0V output voltage converter was selected.

But the noise of the converter appeared in the audio path.

The load current for the output voltage of the converter is not more than 0.5 mA.

I tried using the LDO on 2.8V and it helped a little, the noise became smaller, but they did not disappear, and this is especially noticeable when I remove the input signal and start hearing the high-frequency noise of the converter.

When I looked at the oscilloscope, the output voltage after the LDO became more stable, but the input voltage became noisy.
How can I solve this problem?

Thanks!

over 4 years ago

0 Minqiu Xie over 4 years ago

TI__Mastermind 21565 points

HI Andrew:

The TPS61099x has Burst mode for light load, for save power. And during this mode, the switching frequency will be much lower and it will bring larger ripple.

May I know what's the requirement for the Vout ripple? As I know, the output voltage of the LDO should be stable even the Vin has a ripple.

0 Andrew Bogatov over 4 years ago in reply to Minqiu Xie

Prodigy 20 points

Hello Minqiu:

In my device I use two IC, one is a 2.8V preamp, and the other is OP amp (amplifier) is powered by a voltage of 1.3V, that is, from the input voltage.

Therefore, I have to stabilize both the output voltage and the input

I managed to stabilize the output voltage using the LDO at 2.8V and this can be seen in the figure below.

But how to stabilize the input voltage and get rid of the noises that fall on the input voltage?

0 Minqiu Xie over 4 years ago in reply to Andrew Bogatov

TI__Mastermind 21565 points

Hi Andrew:

Sorry for delay as full schedule these days.

According your waveform. I'm not sure if the result is caused by the ripple or measurement noise. Here is a blog, you could catch the waveform like that. https://e2e.ti.com/blogs_/b/powerhouse/archive/2016/11/29/tips-in-debugging-a-boost-converter

For a boost converter, the easy way to stable the input voltage is enlarge the input capacitance and decrease the parasitic inductance and resistant. You could choose suitable battery, better layout, and add capacitance to improve it.

For output voltage ripple, the burst mode of the boost converter will bring a little large ripple that normal operation. As you may have special requirement for the OpAmp, yes, an additional LDO is a good solution.

0 Minqiu Xie over 4 years ago in reply to Minqiu Xie

TI__Mastermind 21565 points

Hi Andrew:

As long time not hear you, I assume you have solved the issue. I'll close this post. If not, just reply below. Thank you!

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TPS61099: Converter noise gets into the audio path