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TAS5421

Nick Taylor
Prodigy 20 points
Other Parts Discussed in Thread: TAS5421-Q1

Hi,

I have a couple of questions about the load diagnostics function in TAS5421.

1). is the MUTE signal recommended to be in any particular state during load diagnostics ?

2). in our application we de-assert MUTE and nSTANDBY simultaneously and we then see 2 cycles of load diagnostics waveform at the speaker connections (waveform as per fig 11 in the datasheet). It then takes approx 1sec before nFAULT de-asserts and audio is enabled. Is this correct ?

Our application is a warning system and waiting for 1sec after the last load diagnostic cycle is far too long. What can we do to reduce this time ?

regards

Nick 

  • 0
    TI__Mastermind 45085 points

    Nick,

    I need to test this and see why you are seeing such a long time to enable.  It should not do this.

  • 0 in reply to Gregg Scott
    Prodigy 20 points

    above shows a plot of what happens when we come out of MUTE.

    blue and yellow traces are speaker + & -

    red trace is nFAULT

    green trace is MUTE

    There is one cycle of load diagnostics (sometimes we see 2 cycles) followed by 1sec of what appears to be recovery from fault. Finally we see nearly 1sec of our audio. We can live with one or 2 cycles of load diagnostics but it's the 1sec of silence that follows that we need to eliminate. 

    regards

    Nick

  • 0 in reply to Nick Taylor
    TI__Mastermind 45085 points
    Nick,
    After a fault as shown in your oscilloscope screen shot, the TAS5421-Q1 will automatically run Load Diagnostics. If the fault is cleared the device will turn on after a delay of about 700ms, and can be as high as 1 second. We have this delay so that the amplifier cannot enter a mode where a fault would cause the output to chatter on and off very quickly.
    I do not understand why it is turning off again in 1 second. Is this induced by you or is it doing it automatically? If is is doing automatically, you need to look for a DC offset on your amplifier. Especially, look at the input pins. Their DC voltage should be the same value on IIN+ and IIN-.