# TDA7262 Audio Amplfier's SVR/MUTING pin (pin3)

What exactly is the SVR/MUTING pin on the TDA7262?

I've done my research on it but I cant find much. I found something that said its to eliminate the thump the speaker gives off when power is applied or removed to and from the amplifier. I must design a pcb with datasheet specifications but I don't understand pin 3 and the 0.45V.

Circuit attached.

The device is switched off until pin 3 reaches 0.45 to 0.9 V according to the datasheet (V3 = pin3):

You can check TDA7350 for a more thorough explanation on how it is supposed to work. It's not the same IC but the function is similar. You could run an RC filter to the supply voltage to get a power on delay.

The term SVR is the "supply variation rejection" and is usually meant to refer to $k_{SVR}=\frac{\Delta \left(V_+ - V_-\right)}{\Delta V_{IO}}$ -- and it describes how well an opamp, for example, rejects power supply variations when considering its input offset voltage.

The term MUTING here, of course, refers to muting the output of the device.

I think they've managed to combine these two functions into one by using a capacitor. The capacitor has two behaviors: the AC behavior provides the SVR function and the DC behavior provides the muting effect.

When the voltage at the pin is close to ground, the output is muted. As the capacitor charges, it reaches a specific voltage and an internal comparator halts the muting effect. You can mute it again by just discharging the capacitor with a transistor switch, I think.

If pin 3 is disconnected or grounded, the amplifier output is disabled.

If pin 3 is connected to at least 0.45V, the amplifier output is enabled.

Hence connecting 0.45V to pin 3, so you can hear the amplifier.

As to the thump, that requires a sort of logic to make happen. When power is applied, you could hold pin 3 low for x seconds using a RC circuit or a voltage regulator or voltage supervisor or a microcontroller, enough time for the main voltage to stabilize and for the amplifier to be fully on. This is used for sensitive applications or circuit's Where a brown out voltage behavior is unwelcomed. Doing the same when power is disconnected is much more complicated.