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Class D Audio Amplifier IC Forum Discussions

jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

Thank you very much for answering my question!
I use ma12070 to make an audio amplifier and use pbtl mode. Normal operation after power on.
But when I configured the input mode to single ended RCA input, the speaker made a lot of noise. I changed the grounding mode, and the problem remains the same.

I wonder if it is wrong to configure the single ended input mode as shown in the figure below in pbtl mode?

 

11.gif

1 Solution
Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello @jacksl528 ,

Figure 9-5 in the datasheet shows the application diagram for PBTL mode.

Meghana_0-1649821143285.png

 

While mentioning about MSEL0 and MSEL1 pins configuration, i was referring to table 9-1. 

Meghana_1-1649821170193.png

While using single ended inputs, it is essential to match the impedance on both lines of the input as shown below.

Meghana_2-1649821237541.png

 

Please try this and let us know if you still observe noise in your system. 

Regards

Meghana R

 

View solution in original post

10 Replies
Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello @jacksl528 ,

To configure MA12070 in PBTL mode, the configuration bits MSEL0 & MSEL1 pins should be configured as per Table 9-1 in the below datasheet. 

https://www.infineon.com/dgdl/Infineon-MA12070-DS-v01_00-EN.pdf?fileId=5546d46264a8de7e0164b75000286...

 

Technically single ended input can be used in PBTL mode, but it is essential to take care below points

1. Impedance of both input lines should be matched.

2. Input side ground layout should be carefully done so that the there is no noise injected into the input ground. 

Kindly set the configurations pins as mentioned in the datasheet and match the impedance on both the input lines and observe the performance. Please let us know if you still observe the noise. 

Regards

Meghana R

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jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

Hello@
I looked up the example of 9-1 in the data sheet, but isn't this the configuration mode of BTL?

 

 

The data sheet shows:

Pbtl mode (msel0 and msel1 should be grounded)
BTL mode (msel0 is connected to + 5V and msel1 should be grounded)

Can you give me a reference diagram of specific practices? thank you

 

1.gif

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Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello @jacksl528 ,

Figure 9-5 in the datasheet shows the application diagram for PBTL mode.

Meghana_0-1649821143285.png

 

While mentioning about MSEL0 and MSEL1 pins configuration, i was referring to table 9-1. 

Meghana_1-1649821170193.png

While using single ended inputs, it is essential to match the impedance on both lines of the input as shown below.

Meghana_2-1649821237541.png

 

Please try this and let us know if you still observe noise in your system. 

Regards

Meghana R

 

jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

Thank you very much, megana
According to the solution you provided, I joined RS, which really solved my problem.
But if in0a is used as the input of potentiometer, how do I match the impedance??1.jpg

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jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

Using the following circuits, there is still a lot of noise when the front stage is not connected. How to carry out impedance matching?

 

 

112.jpg

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Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello @jacksl528 ,

To eliminate the noise, the inputs should be driven by low impedance source <100ohm or so. This wont be possible if you connect the potentiometer directly on the amplifier input. Instead you can use this potentiometer in the feedback loop of an inverting operation amplifier and connect the output of this opamp to the MA12070 inputs, as shown in below circuit diagram. 

Meghana_0-1650475029554.png

Low output impedance of the opamp will meet the requirements of  low impedance on input lines. With this you can achieve noise reduction and also volume control. 

Hope this helps. 

Regards

Meghana

jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

Hello Meghana

Thank you for your timely reply. Your plan is of great help to me. Thanks again for solving my problem!!

Have a nice day at work!😀

jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

Let me ask you another question:

If the 31st pin (clkm / s) of ma12070 is directly connected to dvdd (5V) without pull-up resistor, will it burn the chip

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Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello @jacksl528 ,

CLKM/S  can be connected to DVDD without a pull-up resistor until the voltage is within the specified limits.

Meghana_0-1650626617654.png

Regards

Meghana R

jacksl528
Level 3
10 replies posted 5 questions asked 5 replies posted
Level 3

I see. Thank you! I wish you every success in your work