Music/ Audio Control

Hi Anurag,

Could you please clarify on the support request?

• Are you trying to replace the functionality of LM4970 with a microcontroller?
• Or are you trying to combine LM4970 with a microcontroller? What do you need the microcontroller to do that LM4970 cannot do by itself?

Best regards,
-Ivan Salazar
Applications Engineer

Yes, I am trying to combine LM4970 with a micro-controller as I only want to control Warm White LED Strip and not an RGB LED strip

Hi Anurag,

I'll discuss this use case along with my team and give you further comments later this week.

Best regards,
-Ivan Salazar
Applications Engineer

Okay, Thank You

Hi Anurag,

After further review of LM4970 documentation, I noticed that RGB module drive is just one of the possible modes of operation, you can connect any other kind of LED to each of the output and it will drive varying duty cycle depending on the audio intensity of each band respectively. This is working the same regardless if its RGB or not. Would this work OK for your application?
Hopefully this clarified the operation of this device, I may not be fully understanding what is your application requirements.

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan,

Thanks a lot for helping me out.
I also read the documentation and I wanted to know if lowband, midband and highband inputs to the micro-controller can drive a single LED Strip or not.
Lets say only a Red Led Strip.
How can I calculate my single PWM output using these three bands.

Hi Anurag,

If you don't need the 3-band feature and just want to use 1 band that covers all the audio content, perhaps you can use the low band output only, and set the low-pass filter to a high value. Based on Figure 12 from data sheet, if you don't connect any capacitor to FILT pin 1 the low pass band would cover almost all the audio band up to 20kHz.

Best regards,
-Ivan Salazar
Applications Engineer

Okay, I will try that. But I right now a capacitor of 1 uF is connected.
What I am doing is, I am not connecting the LED1,2,3 output of LM4970 to any Leds or LED strips directly but I am trying to read those values through interrupt and trying to control different LED strips. The micro-controller that I am using is ESP32 Wrover E.
When I see the waveform using an Oscilloscope, I can see changes in waveform wrt to music at the input of the micro-controller but not at the output.
Is it possible to do what I am trying to achieve? Reading those values using interrupt?

Hi Anurag,

I assume you're trying to use the uC to replicate the PWM output from LM4970 in order to control multiple LED strips, is this correct?
If that's the case, you must make sure that the uC is able to detect the PWM through interrupt, and complete it's processing, before the next event happens, considering the shortest time between events which would be at very low or very high duty cycles from the LM4970.
An alternative could be to use analog buffers instead, you may connect the output from LM4970 to multiple unity-gain amplifiers (buffers). The high impedance input of the buffers should allow you to connect many of them without loading down the PWM signal. In this case you must also consider that slew rate of the buffers must be fast enough to not distort the PWM squarewave-like signal.

Best regards,
-Ivan Salazar
Applications Engineer