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Original question:

TAS5825M: DC Fault description

TAS5825M: DC Fault Solution - Hardware Issue?

Peter Grinalds
Prodigy 90 points
Part Number: TAS5825M

Hello,

We have amplifiers that will go into DC fault 0x70 = 4 at higher volumes. All of our designs do this making us think there is a design error. Could it be that our Output stage caps are too small? Or other reason? Would welcome all feedback. My inductors are 10uH rated to 4.5A and 26 mOhms. My output caps are 220nF but I am seeing an update TI design with these at 470nF. Should I change them?

Additionally, GLOBAL_FAULT1 0x71 = 0x04 constantly but does not seem to impact playback. Is this an issue?

Are there any other fault registers I should be checking?

Best regards,

Peter

Schematic_SVS4_5 Actual_2023-05-21.pdf

  • 0
    TI__Genius 11300 points

    Hi Peter

    can you tell me your PVDD voltage and load resistance?

    can you measure the DC voltage at the output?

    220nF should not lead to this problem. but we recommend you changing that to 470nF.

    tks

    jess

  • 0 in reply to Jesse Ji
    Prodigy 90 points

    Hi Jess,

    Thank you for the help.

    My PVDD is currently set to 5V, but the same thing happens when set to 12, 15, and 20V. The amp faults out sooner at lower volumes with higher PVDD. It will also fault out when I turn up the volume without drivers connected to the speaker outputs. I am setting TAS volume to using both register 4C and also by adjusting volume using I2S volume input. 

    My test bench driver is 4 ohms but faults also occur with 8 ohm speakers connected to each channel.

    I am not sure how to measure DC voltage at the output, but here are the values I am getting:

    • R+ to R- during playback 11mV
    • L+ to L- during playback 2mV
    • R+ to GND during playback 2.81V
    • R- to GND during playback 2.82V
    • L+ to GND during playback 2.71V
    • L- to GND during playback 2.71V
    • R+ to R- without playback 16mV
    • L+ to L- without playback 1mV
    • R+ to GND without playback 129mV
    • R- to GND without playback 144mV
    • L+ to GND without playback 144mV
    • L- to GND without playback 144mV

    Do any of these values fit the need? My system uses USB C power delivery for PVDD and then a DC-DC converter down to 3.3V for the control power.

    On the next iteration I will change the capacitor values to 470nF.

    Best regards,

    Peter

  • 0 in reply to Peter Grinalds
    TI__Genius 11300 points

    Hi,

    1. can you take a try changing 0.22 to 0.47uF to confirm whether this situation still happen or not?

    2. what is the Isat of your inductor? can you share me the PN.

    3. what is your load resistance?

    tks

    jess