TPA3136AD2: OUTPL goes into a "DC" mode when the PVCC is below 9v.

Hi Grant,

Can you give us some more details on the system? Perhaps the schematic? 

The shutdown is a little strange at that voltage level. Where did you measure the PVCC voltage? 

Regards,

Robert Clifton 

I attempted to cut and paste the schematic but am not sure that it got there.  PVCC is measured at that specific pin (28,27 or 15,16)

I see a icon after I did a "snipping tool" copy and paste...... it does not open for me.  Does this open for you?

Note: The Audio starts after the /SD timeout (1.8sec interval)…runs for a bit then the OUTPL goes to DC level which is effectively a dead-short to the speaker which results In the 1.6A spike at which point the /SD goes LOW which shuts the output OFF and then repeats at that 1.8sec rate.

Hello Grant,

It would be recommend to save the image or pdf and upload it either as an attachment or the insert/edit media button in the text editor for e2e. We cannot see the image you posted.

Best Regards,

Luis

........I did attempt to use the "attached" as well as insert.   Neither functioned for me.   Please advise

I have a MSWord document where I cut and pasted the schematic as well as o'scope screen captures.   Can this be attached or uploaded?  If so...how?

Hi Grant,

You can try to insert file.

Maybe your internet has some problem...

I did attempt to "insert".   Did it not work?

Sorry, it still can not work...

Then please tell me how to insert or attach a MSWord document

This does not appear to work to attach or insert a file.   I converted it to a PDF file but this would not "insert" either.

Is there another means to get this issue resolved?    

I am using a VPN connection.   I have disabled this and will attempt to <insert file>    This does not appear to help.......it will NOT complete an "insert"

I have a CASE # for this issue but today is DAY 8 waiting for someone there to reply.   Going to this FORUM has not been useful thus far.

I captured the below picture that how to insert file.

PLimit voltage = 2.7v

PVCC is 9.1 (with two 6ohm speakers attached) is when the OUTPL,NL,NR,PR will begin to go to a DC output of approximately 2msec.  During those 2msec the current draw spikes up to 1.6Amps.   

Note:  If I try to use the little paper clip icon to "Insert File" it does not work.  It will not even let me "browse" to select a file.    Please advise

Is there another means to communicate such as a phone # or an email address?   I would like to be able to move this discussion past trying to get a file or image uploaded to your system.

Regards,

Grant Juel

Oscope AudioAmp-DC mode.docx

Does this folder image actually contain anything?

After rebooting my computer it now appears to work.    NOTE:  The image of the schematic does not show the two resistors (since added) for PLIMIT.  PLIMIT measures 2.7vdc.

5584.Oscope AudioAmp-DC mode.docx

This effect is very dependent upon the "loudness" of the Audio Output.   Thus is seems to be related to the amount of current that the Audio Amplifier is supplying to the speakers.   

Hello Grant,

I noticed in your schematic that the Plimit is left floating, this is not recommend for this device as Plimit is used to limit the output voltage level below the supply rail. In this case the amplifier operates as if it was powered by a lower supply voltage, and thereby limiting the output power by voltage clipping.

If you want the max output power and to not limit the output voltage you should short Plimit to GVDD. Can you short Plimit to GVDD and collect the previously provided waveforms to see if you are observing the same issue.

Best Regard,

Luis

Yes.....  I did add a note to one of the post that stated that I had added back to the PCA the two resistors that set the PLIMIT to 2.7v.    I got feedback on a different post about PLIMIT that I can just tie to GVDD.   

ALL the issue with the "DC" out at lower voltages have been with the PLIMIT properly set.

As noted previously..........I replaced all four inductors with a 3A part.   No improvement noted

Hi,

Please do not connect NC pins to GND, just floating.

And you can remove LC filter(short inductor), RC snubber(2.2nF+47ohm), and try again.

If the issue is gone, then add the bom part one by one.

All NC pins (5,6,13) are now floating (actually the pin is totally removed).   The RC snubber has not been loaded for this build of proto boards (thus already removed).

Only the L (10uH 3amp) and C(2.2uF) are loaded on the output (and the speaker of course).

With the speaker connect or without it connected...........the same results.  The 1600Hz sine wave at the LC junction remains the same.  And that being there is only a GAIN of 10X from the input signal.

The input into the 10uH inductor is a square wave (0-13vpk)  The top of the square wave does decay downward by about 0.5v.

With the L (shorted across the pads) and the C removed (and pins 5,6,13 floating) and the RC snubber not loaded...........the full 13V square wave drives the speaker.

I added the 10uH inductors back but left the C off.  The output signal swings up to the PVCC but is no longer square.   When I add the 2.2uF cap(s) back in then it is back down to the 5vppk

10uH 3A only .docx

Sidenote:

the data sheet shows a UVLO and OVLO.  What are the levels that these function at?

I do not have an EVM board.   I will see if I can locate one to purchase.    I have been working from home this past week.   I will be in the office next week where I can use a Function Generator to provide the sine wave input...........as opposed to the microcontroller's IDAC .

Note:  the EVM board uses only a ferrite for the output filter instead of an inductor.    Could you provide details on how to determine the proper LC for this?    Also......could you address the OVLO and the UVLO levels?

Thanks. 

Hi,

For Gain setting question, you should check voltage difference (OUTP-OTPN) ,not only OUTP/N.

For other questions, I checked the waveform you provided to me, there must OC fault happened.

You can see that when current arrive to one point, fault happened, the PWM switching stopped. 

The difference between beads and LC filter design, you can check 10.2.2 part of datasheet. LC filter can have better EMI performance.

The OVLO threshold is 15V typical, and UVLO threshold is 4V typical, some devices may have a little variation.

Regards,

I tested all of this on a NEW PCA.....where I made pin 5,6,13 all floating.   PLIMIT is tied to GVCC (solder bridge).   The inductors (4) changed to 10uH, 3A parts.  Verified the 2.2uF value for the LC.

The I used a Function Generator to input 800mVppk.......the output was 8Vppk (just before it started to distort.   PVCC was 9v.Sine Input for TPA3136AD2-800mV.docx

It the signal it 8vppk...........would that not mean that it is 4v positive and 4v negative?....therefore the difference between the OUTP and OUTN be 4- -4 = 8v?

Math OUTPR - OUTNR.docx

The ripples were due to the 16K sampling rate from the microcontroller.

I made the changes and the GAIN (using a voltmeter (vrms) shows it at 19.6X.   This is all posted on the CASE for the "GAIN of only 10X" title.

The issue with CLICKING as low voltage is not completely resolved.

This issue is a function of the speaker drive current (the higher the current the sooner it will start to CLICK as PVCC decreases).

The clicking would begin when PVCC was low enougth to show a ripple on the DC voltage.

I did notice that when I added a 470uF cap to the 100uF on PVCC that the threshold for starting the CLICKING lowered.  

I have revised the PCB by having the 100uF cap(s) tie directly to the PVCC and GND without going through any vias.  I also increased the size of the vias to GND for components that directly connect to the Audio Amp.   I also changed pins 5,6,13 so that they all float (not tied to GND).   And I fixed the PLIMIT by connecting directly to GVCC (adjacent pin).   

I will order another round of PCAs to see if these changes eliminate the "Clicking" issue.

Hello Grant,

Thank you for noting the changes, please let us know the test results with the new modified hardware

Best Regards,

Luis

Current into LC.docx

The attached is the current going into the LC filter.   It is stable for the 4.7uH/1.5uF but is NOT with the 10uH/2.2uF   The Switching frequency is NOT looking to healthy with the 10uH/2.2uF

During my continued investigation of this issue.........I noticed that when I touch the /SD with the scope probe that /SD goes LOW (and Audio output turns OFF).  This is observed on two PCAs that I used. 

 /SD has a 102K pullup resistor to PVCC and 1K that connects /FAULT to /SD  and a 1K that connects /FAULT to the microcontroller IO pin (to monitor although no code it written to respond to this input).  

The attached is with using ONLY a function generator to input the Audio Signal.   What I have noticed is that the peak of the Output voltage starts to get "choppy" as the supply amplitude decreases and the input signal large.      NOTE:  The notation on the attached scope images indicates the supply voltage going into the PCA, not the PVCC.   PVCC is regulated to a max of 9v and decreases about 1.5v below the supply voltage to the PCA.

When the "choppiness" occurs I can then decrease the sinewave input amplitude to a point where it will "stabilize".   

At this point in time my "game plan" is to monitor the supply voltage and then limit the input audio signal.   At 11V the MAX GAIN will reduce to 95% of the Full range; at 10V the MAX GAIN will be reduced to 85% of the Full range; and at 9V the MAX GAIN will by reduced to 50% of the Full range.   Typical supply voltage is 12.8V at which point the Audio Amplifier is stable a Full range.   NOTE:  The GAIN is controlled by a digital resistor and Op-Amp prior to feeding the Audio Amp input.

Note:  I also decreased the capacitor for the LC filter from 2.2uF to 1uF.   

SineWave and Reduced Amplitudes.docx

I added a scope shot of the issue that I see when audio amplitude is large and the PVCC is reduced.   I am not concerned with the small ripple frequency that is super-imposed on the audio signal..........but when that small ripple becomes HUGE..........then there is a problem.

0755.SineWave and Reduced Amplitudes.docx

The issue with the audio output going "DC" is due to the OUTPL switching frequency stopping for short periods of time.  See attached document for various scope screen captures.   As the PVCC gets low the clipping results in serious audio noise.   At PVCC = 11v the clipping occurs and the current into the TPA3136AD increases GREATLY as the clipping increases but the audio heard from the speaker does not indicate any issue.   

SineWave and Clipping Amplitudes.docx