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TAS5424A Over-Current Condition

Ben Seaman
Prodigy 70 points

Other Parts Discussed in Thread: TAS5414A

Hi,

We are using the TAS5424A amplifier in our hybrid stepper motor design.  We have the amplifier DC coupled from a DAC and some op-amp filtering/differential amp.

We set up the I2C registers as follows:

        * Clear the faults by reading the fault registers 0x00 and 0x01

       i2c_amp_read_register(TAS5424A_I2C_ADDR, TAS5424A_FAULT_REGISTER_1);

       i2c_amp_read_register(TAS5424A_I2C_ADDR, TAS5424A_FAULT_REGISTER_2);

        i2c_amp_mute_channels(5, 5);

 

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_1, 0x55); // 20db

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_2, 0x0F);

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_3, 0x0D);

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_4, 0x40);

       //i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_5, 0x10);

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_6, 0x00);

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_7, 0x8E);

       i2c_amp_write_register(TAS5424A_I2C_ADDR, TAS5424A_CONTROL_REGISTER_8, 0x3D);

 

       i2c_amp_unmute_channels(5, 5);

 

The problem that we see occurs when the TAS5424A is commanded from Low-Z /muted to unmuted. One speaker output goes to the rail while the other one goes to ground, resulting in an over-current condition. We have checked that the audio input pins are not being driven when this happens. Both pins remain at approximately 3.3 volts dc as they should. It is unclear to me what could cause this behavior. 

Any help/ideas would be greatly appreciated.

Thanks,

Ben

 

 

 

  • 0
    TI__Mastermind 45035 points

    Hi Ben,

    To see if the input is causing the severe DC offset to occur at the output, I suggest that the output filtering of the DAC be removed from the circuit.  Let's make sure your DAC filter is not forcing a DC offset, by forcing current into the input of the TAS5424A.

    I have also seen a dirty pcb around the input pins cause DC offset too.  I would make sure all the flux has been removed from the pcb.

    Please reply with your results.

  • 0 in reply to Gregg Scott
    Prodigy 70 points

    I removed the circuitry input to the AMP and it looks like it is the cause of the issue.  The curcuitry is no longer put into overload mode.  I will invesitage further why this is occuring with our DAC circuitry.  Stay tuned.

  • 0 in reply to Ben Seaman
    TI__Mastermind 45035 points

    The TAS5414A was designed to be capacitor coupled on the inputs.  Do you require to amplify DC in your system?