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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?
Solved! Go to Solution.
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Hello @jacksl528 ,
Figure 9-5 in the datasheet shows the application diagram for PBTL mode.
While mentioning about MSEL0 and MSEL1 pins configuration, i was referring to table 9-1.
While using single ended inputs, it is essential to match the impedance on both lines of the input as shown below.
Please try this and let us know if you still observe noise in your system.
Regards
Meghana R
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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.
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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Hello@Meghana
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
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Hello @jacksl528 ,
Figure 9-5 in the datasheet shows the application diagram for PBTL mode.
While mentioning about MSEL0 and MSEL1 pins configuration, i was referring to table 9-1.
While using single ended inputs, it is essential to match the impedance on both lines of the input as shown below.
Please try this and let us know if you still observe noise in your system.
Regards
Meghana R
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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??
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Using the following circuits, there is still a lot of noise when the front stage is not connected. How to carry out impedance matching?
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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.
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
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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!😀
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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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Hello @jacksl528 ,
CLKM/S can be connected to DVDD without a pull-up resistor until the voltage is within the specified limits.
Regards
Meghana R
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I see. Thank you! I wish you every success in your work