TAS5751M: TAS5751M

Yan Pui Chan

Part Number: TAS5751M
Other Parts Discussed in Thread: TAS5733L

Hi,

I am using the TAS5751M on my custom board and we found one issue during testing. The issue is when increase the input voltage to around 15V the speaker start to has clipping sound. We did couple things to try to resolve the issue and end up removing the 0.68uF capacitors on the output, the clipping sound goes away and I can increase the input up to 21V without any issues. *C22,C23, C25 and C26 on TI's reference schematic.

I am not sure, what is the root cause for this issue. I am thinking that may related to the layout design.

Do you have any ideas how to identify the root cause?

Our application info.

• 4ohm speaker

• 2 layers board

• Components and schematic are following TI's reference schematic (For Stereo Device).

• We are configuring the amplifier to be used in Mono mode - by gang configuring Left and Right channels.

Thanks

over 7 years ago

0 Yan Pui Chan over 7 years ago

Intellectual 510 points

0 Yan Pui Chan over 7 years ago in reply to Yan Pui Chan

Intellectual 510 points

Picture#1 - Low input voltage with capacitors
Picture#2 - High input voltage with capacitors (clipping)
Picture#3 - High input voltage without capacitors
Above results are tested with 1kHz fix frequency

0 Shawn Zheng over 7 years ago in reply to Yan Pui Chan

TI__Mastermind 24835 points

Hi Pui Chan,
Are you using BTL mode or PBTL mode? How much is PVDD? Could you please show me your SCH?When you did this test, the speaker/load is connected to the AMP output or not please? Could you please read the Error Status Register in register 0x02 when the issue occurs? Please make sure the value in the register 0x10 is set to 0x07 to limit the max modulation percentage.
Best regards,
Shawn Zheng

0 Yan Pui Chan over 7 years ago in reply to Shawn Zheng

Intellectual 510 points

Hi Shawn,
Please see the replies as below:-
1. We are using BTL mode.
2. PVDD is 16.5V in our application
3. Schematic attached.
4. Yes, we did connect AMP output to the 4ohm resistor or 4 ohm speaker. Both of them behave the same.
5. The Error status register we saw was 0xD0, 0xC0 and 0x40 when input voltage was high (>15V). When input voltage is low (<15V), the status register was 0x00.
6. The register 0x10 is set to default which is 0x01. We will test the register 0x10 to 0x07 and post the result later today.

Thanks

0 Yan Pui Chan over 7 years ago in reply to Yan Pui Chan

Intellectual 510 points

0 Yan Pui Chan over 7 years ago in reply to Yan Pui Chan

Intellectual 510 points

Hi Shawn,
Update - After we changed the register 0x10 from 0x01 to 0x07, we didn't see any different/improvement.

0 Yan Pui Chan over 7 years ago in reply to Yan Pui Chan

Intellectual 510 points

Hi Shawn,
We did another test by replacing the inductors (L5, L7, L8 and L9) from 1255AY-150M=P3 to 7447709150 and keep the capacitors (C58, C66 C72 and C76), after that the issue goes away.

0 Shawn Zheng over 7 years ago in reply to Yan Pui Chan

TI__Mastermind 24835 points

Hi Yan Pui,

According to the SCH, please make sure the jumper J1 and J2 are set to 1-2 for BTL mode.

From the Error Status Register, there is something problem in the I2S input. TAS5751M is a digital input AMP, so the input signal leve unit should FS, dBFS... I don't quite understand why your input is an analog signal. Is there an Audio DAC in front of the AMP? How much is the reference voltage? Could you please try to use an AP instrument as the input source?

The two kinds of inductors have the same inductance but different saturation current. The Wurth inductors have much higher saturation current. So maybe the Murata inductors in the output filter are saturated by the very large output current and the device gets into protection mode to avoid device damage.

Best regards,

Shawn Zheng

0 Yan Pui Chan over 7 years ago in reply to Shawn Zheng

Intellectual 510 points

Hi Shawn,
1. Yes, JP1 and JP2 are set to 1-2 for BTL mode.
2. We are using digital signal, not analog signal.
3. Do you have any suggestions for the inductor other than the Wurth one. Prefer to have smaller package?

Thanks

0 Shawn Zheng over 7 years ago in reply to Yan Pui Chan

TI__Mastermind 24835 points

Hi Yan Pui,
7447709150 is good choice, we used it on many EVM board(e.g. TAS5751M, TAS5733L...). Usually very small package inductors can't support high current. I'm not an expert in inductor, you could contact with Wurth/Murata product engineer.
Best regards,
Shawn Zheng

0 Yan Pui Chan over 7 years ago in reply to Shawn Zheng

Intellectual 510 points

Hi Shawn,
Just curious - If the issue is related to the inductor spec., why I am getting the error messages that relate to I2S signal?
One more test we did is measure the current through the inductor and the current can raise up to ~4.25A when input voltage at 20V. The over current for TAS5751M is 4A, it seems make sense the over current protection will take action?

0 Yan Pui Chan over 7 years ago in reply to Yan Pui Chan

Intellectual 510 points

0 Yan Pui Chan over 7 years ago in reply to Yan Pui Chan

Intellectual 510 points

Attached is the current through the inductor when input voltage at 20V.
Thanks

0 Shawn Zheng over 7 years ago in reply to Yan Pui Chan

TI__Mastermind 24835 points

Hi Yan Pui,
Thanks for your measurement. The 4A OC THR data in the datasheet is the typical value not min value. It's expected that the OC THR has variation around the typical value.
Best regards,
Shawn Zheng

0 Shawn Zheng over 7 years ago in reply to Shawn Zheng

TI__Mastermind 24835 points

Hi Yan Pui,
I'm closing this question. Please feel free to create a new post if you have more other questions. Thank you!
Best regards,
Shawn Zheng

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TAS5751M: TAS5751M