MAX9768 cannot MUTE

Question

hello 
 I have implemented MAX9768 for voice guidance on a microcontroller board PC that I designed. When I connected a speaker and input voice data, it was able to speak. The volume is controlled by I2C, and the MUTE pin is also connected to GPIO for control. 
 Even if this MUTE pin is set to high level, the volume is reduced, but it cannot be completely muted. The same is true when the volume data is minimized via I2C. Is there any possible cause for this?

Ichiemo · Accepted Answer

Hello. Thank you very much for your answer. I understood that the mute function of the MAX9768 attenuates greatly, but does not mute completely if the analog input signal is large. 
 For the audio signal on our board we use the sound output "MQS" of the i.max6ull microcontroller. 
 The volume control is controlled by i2c. This volume is also very loud at the step from level 0 to 1. As you say, the original analog signal may be too loud. I will check it out. In addition, if our system does not need any audio output at all, we will consider using the /SHDN pin.)

EdSellers · Answer

Hello, Ichiemo, 
 The MAX9768 Mute feature is effectively a heavy attenuation setting. The outputs do not stop switching when the Mute is enabled, but the attenuation is high. I just measured the Mute performance on the bench, and I get -120dB of attenuation using the MUTE pin or the I2S Mute setting. 
 If the analog input signal is large, at 1Vrms, the output signal may still be around -100dB while the device is muted. This would still be a very small signal, but depending on the application, it may not be enough attenuation. 
 If no output signal at all is desired, the MAX9768 output can be disabled by using the /SHDN pin, but it is recommended to use the MUTE pin while toggling /SHDN high or low. 
 
 Please let me know if you have any further questions. 
 Ed S

Electronic Design Services - PartnerZone

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MAX9768 cannot MUTE