Reverse engineering a car radio amp IC

[Nickk2057]

Hello all to our remarkable engineers.

I have been trying to find out how to turn on this amplifier IC but could not find out how. This is a TDA7850A chip. It is at a total of 200W combined watts with all channels driven. I looked at the scamatic of this IC but could not find out what it means for input high or input low for the standby pin and the mute pin. Help would be great. Thanks.

PS. The images from my phone was too large. Will have to resize them when I get home.

[capt bullshot]

It's all in the datasheet, p. 8:

http://www.st.com/content/ccc/resource/technical/document/datasheet/24/f1/fe/de/11/c2/4d/15/CD00173410.pdf/files/CD00173410.pdf/jcr:content/translations/en.CD00173410.pdf

Low level means mute / standby, high level means "let's make some noise".

[Nickk2057]

But what does it mean? Am trying to figure this out and it is rattling my noggen.

[stj]

low = ground, high = the supply voltage - or more usually anything over a few volts.

[Zero999]

But what does it mean? Am trying to figure this out and it is rattling my noggen.

As mentioned above: it's all in the data sheet. See page 8. Standby out threshold voltage (Amp: ON) 2.75V, Standby in threshold voltage (Amp: OFF) 1.5V.

Beware of the maximum output power specification, which is quoted when the output is a square wave, which bears no resemblance to music or voice! It will be a horrible buzzing noise. The power output with virtually imperceivable 1% distortion is half the maximum power output specification.

[Nickk2057]

So basically it has to be anywhere around 2.75V to actually turn on. Would a resistor across the supply suffice?

[Zero999]

It's all on the data sheet. Refer to page 12, section 4.3 "Standby and muting"