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ebeinongmin
Level 1
5 sign-ins First reply posted First question asked
Level 1

hi,we have encountered the click noise issue when press power off key to power off the unit in standby mode (no audio played this time), the irs2092 circuit is same as application note description. from the application note we know this chip have the click noise elimination function when power off, please advice why still occur the pop noise from speaker output of Tweeter, thanks.

pop noise when power off 1.pngpop noise when power off 2.png

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1 Solution
Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello ebeinongmin,

Thank you for posting on Infineon Community.

We understand that you are experiencing a clicking noise at turn-off of irs2092.

Firstly, we would like to know the following:
-Let us know the background of the oscilloscope captures, details on the testing conditions between image 1 and image 2.
-What are channels 1, 2, and 3 measuring in the captures?
-Is there any deviation in your circuit from the schematic shown in the datasheet/app note?

Please note and confirm that the following points are met, as described in the app note:

1. CSD pin has a slow enough ramp up from Vth1 to Vth2 such that the voltages in the capacitors can settle to their target values.
2. High side bootstrap power supply needs to be charged up prior to starting oscillation.
3. Audio input has to be zero.
4. For internal local loop to override external feedback during the startup period, DC offset at speaker output prior to shutdown release has to satisfy the following condition.
DCoffset < 30μA × Rfb

Looking forward to your reply.

Best regards,
Pablo

View solution in original post

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13 Replies
Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello ebeinongmin,

Thank you for posting on Infineon Community.

We understand that you are experiencing a clicking noise at turn-off of irs2092.

Firstly, we would like to know the following:
-Let us know the background of the oscilloscope captures, details on the testing conditions between image 1 and image 2.
-What are channels 1, 2, and 3 measuring in the captures?
-Is there any deviation in your circuit from the schematic shown in the datasheet/app note?

Please note and confirm that the following points are met, as described in the app note:

1. CSD pin has a slow enough ramp up from Vth1 to Vth2 such that the voltages in the capacitors can settle to their target values.
2. High side bootstrap power supply needs to be charged up prior to starting oscillation.
3. Audio input has to be zero.
4. For internal local loop to override external feedback during the startup period, DC offset at speaker output prior to shutdown release has to satisfy the following condition.
DCoffset < 30μA × Rfb

Looking forward to your reply.

Best regards,
Pablo

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ebeinongmin
Level 1
5 sign-ins First reply posted First question asked
Level 1

Hi Pablo:

     thanks for your quickly response for this issue, please refer to reply as below FYI, thanks.

1.  for channel 1 of image 1:  the PWM signal waveform at Speaker output (Single End for Tweeter output) and have no audio signal input;

2. for channel 2 of image 1:  the PWM signal waveform at Speaker output (Single End for Tweeter output) after through 20KHz filter at oscilloscope and have no audio signal input;

3. for channel 3 of image 1:  the waveform for CSD when power off via press power button.

4. attached is the AMP circuit section for our applying for your reference.

5.  according the datasheet/app note,  

1). CSD pin has a slow enough drop down from Vth1 to Vth2.

2).  not sure how to make sure the high side bootstrap power supply needs to be charged up prior to starting oscillation as this issue just occurred during power off mode;

3). Audio input has to be zero: yes as this issue just occurred during power off mode and no audio input;

4). the DC voltage is 7mV around for Tweeter (SE configuration);

6. just clarify, it have no click noise during power on and Power off when plug off the AC source, it just only occurred during press power button to power off the unit (the MCU will pull down the CSD pin slowly);

irs2092 pop noise elimination boot squence.pngTW SE configuration for AMP circuit 1.pngTW SE configuration for AMP circuit 2.png

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello ebeinongmin,

Thank you for your response.

I understand that you are experiencing a clicking problem when pulling down CSD.

From your schematics, I can see that the design deviates from the reference in the datasheet/app note.
In the topic of CSD, I assume that you are using EXT_SD to pull down the pin.
As far a the CSD waveform is concerned, the slope looks slow enough.
However, please try changing the pull-down resistance and see if the click noise changes.

Also, please confirm that this noise does not originate from the input or other peripheral circuits such as the microcontroller.

We are working on your issue internally.
Let us know if there are further findings.

Best regards,
Pablo

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ebeinongmin
Level 1
5 sign-ins First reply posted First question asked
Level 1

Hi Pablo:

we have change the pull down resistance of CSD from currently 220ohm to 0ohm, but the click noise still existed when power off  the unit. and also changed this resistor from 220ohm to 1kohm, the CSD waveform can be slow enough from 2mS to 6mS, seems the click noise can be smaller than before but still can audible, 

then we tried to change the switch frequency from currently 359KHz to 418KHz, no more improvement for this audible click noise.

please advise, thanks.

PRX900 TW Click Noise issue with CSD series 1kohm-359KHz.pngPRX900 TW Click Noise issue with CSD series 220ohm-408KHz.png

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ebeinongmin
Level 1
5 sign-ins First reply posted First question asked
Level 1

Hi Pablo:

we have tried to do some changes for the LC configuration but no more improvement to eliminate this click noise when power off the unit, but we can find the function that this irs2092 have the "click noise elimination " during power on or power off; below are the details action FYI, please advise asap, it is urgently for us to launch the product to mass production, thanks for your supports.

  • tried to change the switch frequency, it has no more improvement and high frequency will cause the EMI issue, so we will keep currently switch frequency (360KHz) with no change;
  • tried to change the RC C272 from 0.01uF to 0.1uF or NC this cap, no more improvement for this click noise;
  • tried to remove the 2nd LC filter (L6 and C19), no more improvement for this click noise;
  • tried to change the capacitance for C273 from 0.33uF to 1uF, no more improvement for this click noise but can reduce the Vpp for TW output PWM level;
  • for CSD series 1kohm resistor to instead 220ohm, it can be reduce a little more click noise when power off, but it has tiny click noise when power on;
  • TW SE configuration for AMP circuit 3.png
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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello ebeinongmin,

Thank you for sharing details on debugging.

At the moment we do not have a solution for you.
But be sure that we are working on this issue.
I understand that this issue may affect the mass production of your product.

I will let you know when we have an answer for you.

Best regards,
Pablo

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello ebeinongmin,

Could you please try the following test on your side?

-Short class D input to GND.
-After this, pull down CSD pin.
-Check for click noise.

With this test, we want to confirm if the issue comes from the previous stage.

Let us know about the results of the test.

Looking forward to your reply.
Best regards,

Pablo

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ebeinongmin
Level 1
5 sign-ins First reply posted First question asked
Level 1

hi Pablo:

thanks for your comments, after short the irs2092 input to GND then power off the unit, still can heard the click noise, please refer the test waveform (CH2) FYI, please advise, thanks.

ebeinongmin_0-1639036992495.png

 

 

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello ebeinongmin,

Thank you for your cooperation.

We understood that the problem persists.
Therefore the issue is unrelated to the input stage.

Next, we would like to evaluate the CSD pin.
Could you let us know how the pin is being pulled down?
(Microcontroller pin, transistor, etc.)
The purpose of this is to know if there is any common GND impedance between where the CSD is being pulled down and the actual analog GND.
It would also help us if you could measure this impedance.

Best regards,

Pablo

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kaitlyn
Level 1
First reply posted Welcome!
Level 1

Hi Pablo

we control the EXT_SD pin to pull down the CSD through MCU AMP_MUTE PIN

kaitlyn_0-1639114404468.png

 

 

 

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello kaitlyn,

Thank you for the clarification.

From the schematic, I can now see that CSD is not being pulled to VSS level, but to -5V.
It is being pulled to -5V.

Could you try the following:
-Short CSD and VSS with a 10k resistor manually.

If the click noise disappears we can isolate the pull-down side as the problem.

Let me know about the result.

Best regards,
Pablo

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kaitlyn
Level 1
First reply posted Welcome!
Level 1

Hi Pablo

You mean VSS was the +5V? if so, it still can hear the noise by ear at power on and power off, if no, please tell me detail , thanks 

kaitlyn_0-1639130047113.png

 

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello kaitlyn,

Thank you for the clarification.

From the schematic, I can now see that CSD is not being pulled to VSS level, but to -5V.
My previous comment was simply a confirmation that in your schematic VSS is being pulled to -5V, not GND.

My next suggestion is the following:
-Short CSD and VSS with a 10k resistor manually.
This means to physically connect a 10k resistor from CSD to VSS, without microcontroller intervention.
This can be performed by either connecting one end by hand to VSS when wanting to turn off.
Or by installing a manual switch that pulls CSD via the 10k ohm to VSS physically.
Please refer to the attached image as a reference.

manualswitch.png

If the click noise disappears we can isolate the pull-down side as the problem.

Let me know about the result.

Best regards,
Pablo

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