Bypassing TPA6141 during passive mode for BT headphone

Eng Lih Khaw

Expert 2000 points

Other Parts Discussed in Thread: TPA6141A2

Hi,

I've an inquiry regarding the TPA6141.

Background: The application is BT headphone and also support direct line-in from headphone jack. During active mode (BT enable, power on), audio signal will route to the IC. And in passive mode (user plug in the headphone jack, BT disabled), the audio signal is bypassing the IC as shown in the diagram below:

I've two questions:

1. Is this IC able to support/working in this connection?

2. If yes, what is the absolute maximum rating at OUTR/OUTL before breakdown? (Audio input from passive mode is 1Vrms)

over 11 years ago

0 Don Dapkus over 11 years ago

TI__Guru**** 189401 points

Hi, Khaw,

I don't understand why you would want to do this, you lose all the benefits that the TPA6141A2 brings to your system...

Disable the amplifier, and the outputs are high impedance. However, you will not be able to have an output swing greater than one diode drop below ground. But, this should be enough to get the 1 VRMS swing that you are looking for.

-d2

0 Branden Sheffield over 11 years ago in reply to Don Dapkus

Prodigy 20 points

Don,

I have the essentially the same application. The desire is if the battery is dead the BT headset could still be used passively (a hard wire aux input connection from the music source).

Do the amplifier outputs go high impedance even if the power supply if off? would the maximum voltage swing still be 1 VRMS? Or would you recommend using an external circuit to switch the outputs?

I am incredibly tight in both space and my power budget so I would like to have a minimal solution.

Thanks!

0 Don Dapkus over 11 years ago in reply to Branden Sheffield

TI__Guru**** 189401 points

Hi, Branden,

We will have to investigate this. I am concerned that if the power supply has been removed, the outputs will be in an unknown state. And, we also have to worry about ESD cells clamping the audio signal as well, so you can see this is a complicated use case...

-d2

0 Matthew Beardsworth over 11 years ago in reply to Don Dapkus

TI__Genius 9175 points

Hi Khaw and Branden,

I have tried this use case the lab with a TAP6141EVM and have confirmed that using the part in this manner for both Shut Down mode and power disconnected will work.

I have only tested up to 1.5VRMS and cannot confirm that it will work at higher voltages.

First plot is in SD both measuring and generating a signal on the HP output.