TPA6211A1-Q1: Abnormal output in SHUTDOWN mode

Hello, 

Our team is looking into this thread and will respond as soon as possible. 

Best Regards, 

Justin Beigel

Hi Jiawei,

Could you please also capture the shutdown pin status during power up? This is just to double check this signal and make sure it's low.
Is it possible to disconnect shutdown pin from the host controller? There is an internal pull-down resistor that can be used to check if the transient can be cause by external connection.

I noticed shutdown signal mention TAS2505 on the schematic, is this signal being shared by different devices?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

As you said, there is an internal pull down resistor. If customer disconnect shutdow pin with host controller, shutdow pin also keep low due to the pull down resistor. Is that make sense? I will double check the waveform, but could you kindly tell me another direction to debug this case? Thanks!

B.R. 

Jiawei

Jiawei,

Yes, disconnecting it from host would allow internal pull-down to shutdown the device during power up. Just wanted to double check.

The other factor I think could affect here is bypass capacitor. Bypass capacitor sets the charge ramp during power up, if capacitor is small, or no capacitor is used, the ramp will be fast. This in combination with single-ended input could cause impedance mismatch at the inputs, and capacitor charge time to cause transients.
In order to test this case you can use a bigger bypass capacitor, 1uF or similar. This would give more time for all the signals to settle before device becomes completely active.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

Thanks for your reply first!

Customer double checked the shutdown pin, and make sure that the pin is lower than 0.2V always.

1uF bypass capacitor seems no work, the pulse still exists. So any other debug directions? Appreciate for your support!

B.R.

Jiawei

Hi Ivan,

Do you have another debug directions? Many thanks!

Hi Jiawei,

I'll try similar test on my side, using an EVM. If not able to replicate will focus on what could be the difference causing this.
No further ideas right now to find the root cause.

Best regards,
-Ivan Salazar
Applications Engineer- Low Power Audio & Actuators

Jiawei,

I was not able to replicate using an EVM.
Have you tried to isolate the amplifier from previous and next stages? eg. audio source and speaker connection.
Perhaps there is some artifact at the input of the device that is coupling to the output trough feedback resistors.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

Thanks for your support. My customer re-product the mistake in the EVM. Let's communicate in the e-mail. Thanks!