Line output transient jump

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Hello All,

 

I am currently working on a project dealing with a TLV320AIC23B. When I turn all power on and monitor at the line output pin, I see a sudden jump of about 0.2V to 0.3Vdc then logarithmically rise to 1.66 Vdc (which is right for the Vref). I wonder if there is anyway I could get output at the LOUT pin offsetting slowly (or if it is possible at all).

 

I do really appreciate for any response.

 

Best regards,

Dara

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The behavior you describe is not a big surprise. The fact that it has an internal High Pass function will only emphasize such events. I see nothing in the spec sheet about power-up behavior.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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I do really appreciate your response, Jim.

 

I understand that; however, this behavior will produce a bumping for an audio signal. Is there any thing we can do firmware-wise to help prevent this issue?

 

Btw, have a good weekend.

 

Best regards,

Dara

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What is the output connected to?  You could put a relay in series with the output that has a 200 millisecond or whatever you need delay to energise.  THis way it gives the TLV320AIC23B time to stabilise.

 

Another Jim

If you want a career with a known path - become an undertaker. Dead people don't sue! - Kartman

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

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I do not know any detail about that chip so cannot help you on that.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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I've not used that chip, but a quick look at the data sheets shows that the Mute function is software controlled, so you can't Mute the output via an external Pin on power up.

 

If you are capacitively coupling to the next stage then one could put a small NFet on the output of the cap and hold the output low during the start up with a pull down resistor on the Gate, and then Gate control when the micro powers up, (if this project has a micro...).  Releasing the output of the cap it can then charge up to Vcc/2 via two, high valued resistors, and the output will rise to Vcc/2 slowly.

(Audio feeds cap which feeds into a resistor divider, which then feeds the next stage).

 

Note that any audio applied before the cap output floated to Vcc/2 would be clipped on the negative peaks, and therefore distorted, (briefly).

 

If the output can tolerate a current limiting resistor, then again one could pull the signal down with a small NFet, (chip to resistor to NFet and to next stage).  This is trickier both because of the added output impedance, and because with the cap you control the rise time, with the resistor the internal circuit will equilibrate, and you only wish to forcefully mute the initial glitch.

 

Another option, of course, is to send an eMail to TI's tech support, and ask them how to mitigate the startup glitch induced audio click.

 

JC

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The line output is connected to a highpass filter then goes to an amplifier, so the transient at startup would not be safe for a device that is connected to the amplifier.

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dararos wrote:
this behavior will produce a bumping for an audio signal

Of course it will - this is very common.

 

This is why many audio amplifiers have "anti-thump" features ...

 

Google "anti-thump", "anti-pop", "pop-free switch", etc, ...

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dararos wrote:
TLV320AIC23B

That's a TI product - so why not ask in the TI forums?

 

On the TLV320AIC23B product page - http://www.ti.com/product/TLV320... there is a link for 'Support & training' 

 

that will take you to the TI Audio Converters Forum

 

https://e2e.ti.com/support/data_converters/audio_converters/

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Thanks you. I haven't thought of this forum before.