TAS2770: TAS2770 Open load detection circuit

Hi Ivan, 

Thanks for the appnote. 

From the Appnote suggested regarding open circuit detection, I am using Diagnostic Circuit #2 with BJT and MOSFET suggested for TAS2505-Q1 amplifier.

The suggested amplifier IC has a GPIO pin as given in appnote, but we are using TAS2770 amplifier, which does not contain the GPIO Pin, so we are using micro-controller GPIO Pin is used for output and Input. Attached the circuit for reference.

Here we try the two types of configuration. We are expecting to achieve configuration, but audio was not able to detect.

Configuration 1:

1. Make TAS2770 to play
2. Mute the amplifier
3. Verify short circuit of speaker terminals
4. Then verify the open circuit
5. Unmute the amplifier

This behaviour happens as expected.

Configuration 2:

1. Mute the audio amplifier

2. Then verify the open circuit

3. Unmute the amplifier IC

4. Make TAS2770 to play – But audio was not detected

The actual working scenario should be as configuration-2 whereas we are facing issue in it.

Kindly let us know how to address/debug the issue in 2nd configuration.

Hi Anjanaa,

Can you explain further the differences on config 1 vs config 2? Is it only config 2 does not have step 3 from config 1?

Can you read registers 0x24, 0x25 and 0x26 to check if there is any flag being triggered?

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

Hi Ivan, 

Can you explain further the differences on config 1 vs config 2? Is it only config 2 does not have step 3 from config 1?

State of Registers 0x24, 0x25 and 0x26:

While increasing the delay from 350ms, the audio cannot play. 

Above 350ms delay, checked the register values, 

Register values are:-

PWR_CTL - 0x00

MISC_IRQ - 0x80

INT_LIVE0 - 0x04

INT_LIVE1 - 0x00

INT_LTCH0 - 0x04

INT_LTCH1 - 0x00

INT_LTCH2 - 0xC3

Thanks, 

Anjanaa

Anjanaa,

From register INT_LTCH0 = 0x04, it seems there is TDM clock error. Can you scope your SBCLK and FSYNC to check if these signals are missing at one of the steps you listed?
If these signals are missing at some point, you could try to disable the device (using register 0x02) before the signals are missing, and re-enabling the device after these signals are back.

Not sure if it's just a missing step, but in step 1 it is "Mute device" but I don't see any "Unmute device" step prior to "6) Play the audio"

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