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TDA7391 MUTE and SYNC pins

Question asked by lnmaurer on May 11, 2015
Latest reply on May 12, 2015 by zhao.yuntao
The TDA7391 (datasheet) has two pins that are named MUTE and SYNC. SYNC is supposed to be connected to ground through a resistor (named R2), and MUTE is supposed to be connected to a capacitor (named C3). The datasheet notes that: "The values of C3 and R2 determine the time required to bias the amplifier."

The datasheet has an example circuit (Figure 3 in the datasheet) which shows R2 as 56 kOhm and C3 as 33 F. I think that last number must be a typo.

Does anyone know what a good value for C3 is? Does anyone know how exactly the values of C3 and R2 determine the time required to bias the amplifier? Is it just the RC time?

For what it's worth, the datasheet for the TDA7391LV (a similar device) has a R2 of 220 kOhm and a C3 of 2.2 uF in its example circuit. That datasheet also notes: "The suggested values of C3 and R2 define the correct timing in order to switch on/off the amplifier without any pop noise." However, the datasheet still does not say how R2 and C3 were chosen.

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