BQ24715 noise and GUI download for EVM

Thomas Bombard

Other Parts Discussed in Thread: BQ24715, BQSTUDIO

A customer is evaluating the BQ24715 using the EVM and has noticed an audible noise issue. Here is the input from the customer :

So we have been chasing some audible noise coming from the battery charger for a few days now. We are now able to recreate it with EVM feeding our system. if there is a static load the EVM is quite once we attach to our system (dynamic load, mother board with uP) the humming comes back. Any suggestions on ways to mitigate the noise?

Also, the User's Guide for the EVM references a GUI, but there is no S/W to download for the BQ24715EVM. BQStudio does not seem to support this device. Where can the referenced GUI be downloaded?

Thanks for your help!

9/9/15[LE]>also comment about snubber circuit on EVM; will this be helpful in this case?

over 8 years ago

0 Wang5577 over 8 years ago

TI__Guru 56650 points

bq24715EVSW.zip

0 Wang5577 over 8 years ago in reply to Wang5577

TI__Guru 56650 points

The previous attached zip file is the bq24715 GUI. For audiable noise: What is the system load transient frequency? If the frequency is 20~20k Hz, we may hear it.
The noise could come from the input and output ceramic capacitors. Could they try to replace some ceramic capacitors to electrolytic capacitors or add some electrolytic capacitor to reduce the low frequency ripply in the ceramic capacitor?

0 Wang5577 over 8 years ago in reply to Wang5577

TI__Guru 56650 points

Switching node snubber reduces the cycle by cycle ringing which has a high frequency. I don't think the switching node snubber can fix the low frequency audiable noise.

0 Joseph Narciso over 8 years ago in reply to Wang5577

Prodigy 40 points

The EVM doesn't have any ceramic output caps installed. I did add a 100uf electrolytic to C26 without any effect.

0 Wang5577 over 8 years ago in reply to Joseph Narciso

TI__Guru 56650 points

Do you add DC load or a transient load on EVM output? Do you enable charge?

0 Wang5577 over 8 years ago in reply to Wang5577

TI__Guru 56650 points

On EVM, the output capacitor C16 and C17 both are 10uF ceramic capacitor; the input capacitor C2 and C3 also are ceramic capacitor.

0 Joseph Narciso over 8 years ago in reply to Wang5577

Prodigy 40 points

We added a transient load to the EVM sys output. I have tried with both charge enabled and disabled.

0 Joseph Narciso over 8 years ago in reply to Wang5577

Prodigy 40 points

Yes, i missed that thanks. Do you recommend removing the ceramics and adding electrolytic caps instead?

0 Wang5577 over 8 years ago in reply to Joseph Narciso

TI__Guru 56650 points

If the tranisent load frequency is 20~20k Hz, it can generate a low frequency ripple on the charger power components: FETs, inductor and capacitors. Another idea is adding enough system capacitor to reduce the load transient to the charger circuit. But, you already tried 100uF.
According to my experiance, the ceramic capacitor could be the noise source. So, replace them until we find where the audiable noise come from.

0 Joseph Narciso over 8 years ago in reply to Wang5577

Prodigy 40 points

Replacing the input ceramic capacitors with tantalum seemed to help the noise issue greatly. Thanks.

0 LeonardEllis over 8 years ago in reply to Wang5577

TI__Guru 71516 points

The noise was significantly reduced when the SW Freq was changed from 1MHz to 600kHz. Is there a compensation network required on the BQ24715 that might improve the noise generation at 1MHz?

0 Wang5577 over 8 years ago in reply to LeonardEllis

TI__Guru 56650 points

Would you compare and share the 1M and 600kHz waveform (input current, switching node voltage, system load transient current, inductor current)?

bq24715 has integrated compensation network. It doesn't require external compensation circuit.

0 LeonardEllis over 8 years ago in reply to Wang5577

TI__Guru 71516 points

Noise was reduced by changing the filter capacitors on the regulators to Aluminum NH poly

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BQ24715 noise and GUI download for EVM