TLV62565: TLV62565DBVR is tiny noise sound when is running Softstart time.

Hi Gerald,

you are using a 5.6uH inductor which is not a recommended value.
Please use an inductor with 2.2uH (see table 2 in the data sheet).
C135: please change the feed forward capacitor to 8.2pF.

Best regards,
Ivo

Hi Ivo

Thank you for your fast reply

We test that used inductor with 2.2uH and capacitor with 8.2pF as well as revome to reduce ripple circuit.

However, we didn't good result which same result that noise sounds like Pop-up noise when is softstart time.

Can we get more information and solution?

Best Regards

Gerald choi

Hi Gerald,

do you mean there is an acoustic noise you can hear when powering up the converter?
Beside VIN and SW node, can you please also show the inductor current when powering up the device?
Looks like the input voltage (VIN) is ramping up slowly (10ms ramp time) - can you try to ramp VIN faster?

Best regards,
Ivo

Hi Ivo

Yes, We heard acoustic nosie when powering up the converter.

We try to ramp Vin fastly remove cap for Vsys.
However, We can't slove your solution.

Can you have solution and more information?

Best Regard
Gerald.choi

Hi Gerald,

do you power up and power down the converter continuously when you hear the noise ?
If the power up/down frequency is within the audible range (1kHz to 20kHz), then this would explain the noise.

Are you powering up the converter under heavy load conditions?
Do you know which passive component(s) producing the noise: input or output capacitor, inductor?

In order to check the correct functionality of the converter can you please send a scope plot of the power up event with following probes:
- input voltage
- output voltage
- SW pin
- inductor current

Best regards,
Ivo

Hi IVO

Thank you for your replay. 

We can heard like pop-up noise when power up and power down.

And then, We might hear When change mode PSM to PWM and PWM to PSM mode   

 

Even, We can hear acoustic noise at the TLV62565EVM-179 board

-In & Output Voltage is as a chart below 

  IN(CH1) Voltage: 4.4V, Out(CH2) Voltage: 3.3V 

 

-SW PIN

-Inductor current: 265mA

Can we get more solution and information? 

Best Regards

Gerald

Hi Gerald,

your plot shows a switching frequency of about 1.3MHz, so the converter and passive components cannot be the audible noise source.

Typically TPS62565 switching frequency is above 20kHz for load current greater than 2.5mA (Vin = 4.4V, Vout = 3.3V, 2.2uH inductor).
So in theory there is only noise in case of very light load conditions (< 2.5mA).

Can you please provide information about load?

Another reason for noise is pulsed load current in the audible frequency range.
Could this be the reason for the audible noise?

Best regards,
Ivo

I forgot to mention, that typically during softstart time there are no switching pulses in the audible range.
However when soft start is over and the load condition is <2.5mA, there could be a PFM switching frequency <20kHz - as mentioned above.

Best regards,
Ivo

Hi Ivo 

Thank you for your reply kindly.

I used TVL65565DBVR for STM32F429 on ST MCU. 

We tested result that normally load current is 265mA and Max Current is 420mA. 

We can hear power up & down and when might change PFM to PSM mode. 

We didn't know exactly reason for the audible noise. However We can hear the audible noise on TLV62565EVM-179 board

If you have any question. anytime contact me.

Best Regards

Gerald