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Original question:

TAS5825M: High idle current and missing SDOUT

TAS5825M: high idle current, inductors getting hot

James May
Prodigy 135 points
Part Number: TAS5825M


Tool/software:

This is a follow on to a previous thread. I had originally seen high idle current (with clocks present), and very warm inductors, with or without speaker load attached. After setting the modulation to 1SPW, 768KHz, the current went down to an acceptable level, and the inductors and chip were no longer hot.

However, now when I go back to BD 384KHz modulation, the chip gets hot but the inductors no longer get hot as they once did. Furthermore, I have a colleague who is experiencing both a hot chip and inductors even when set to 1SPW, 768KHz.

So, what besides the modulation setting, could be causing the hot inductors? Is there some other setting, mode, configuration, or power supply conditions that could cause this? I am using 24V and 3.3V.

James

  • 0
    TI__Mastermind 19880 points

    Hi James,

    Are you seeing the temperature get hot with no load and no input signal? Or are you sending some input signal and in that case what is the load?

    Could you help to share layout and schematic?

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    Prodigy 135 points

    Hi Sydney,

    The temperature gets hot with or without a load, both inductors and chip, but only if clocks are present per my message. The question boils down to what could cause this if it is in the low power 1SPW mode, and why it does it sometimes exhibit the heating but other times not?

    I've attached a schematic. I could provide a layout if need be.

    James

    C16780_1_bw XPatch 1 amp page only.pdf

  • 0 in reply to James May
    TI__Mastermind 19880 points

    Hi James,

    Please allow me a day to review the schematic. If you can also share the layout that would be great. 

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    Prodigy 135 points

    Hi Sydney,

    I'll send the gerbers but prefer to do it over email. Please ping me james@jamesmayengineering.com

    James

  • 0 in reply to James May
    TI__Mastermind 20541 points

    hi James

    sorry for jump in.

    can you check you inductor whether it meets below request in our DS?

  • 0 in reply to Jesse Ji
    Prodigy 135 points

    Jesse,

    It is the same inductor used in your reference EVM board. Are there other factors that need to be taken into account? Also to reiterate, it doesn't always get hot. If I use BD mode, the inductors (and chip) get hot even with no signal or load, if there are clocks. The same is true for the EVM. If I switch to 1SPW mode, the problem goes away, both on the EVM and on my board. So that is okay. BUT, my colleague is getting hot inductors and chip even when in 1SPW mode, on the same board, but with slightly different environment. We don't understand why. I'm trying to reproduce his issue here, and have slowly been eliminating differences between his environment. In both cases, the same config file is being loaded into the chip at startup, with 1SPW mode set.

    I think the essential question is are there some other startup or other conditions that might put the chip into a mode that heats up the inductors.

    James

  • 0 in reply to James May
    TI__Mastermind 19880 points

    Hi James,

    The inductors used on the EVM may or may not work with your use case. The equations from the datasheet should be used to ensure the inductors are rated properly. If the inductors are rated too low they will saturate and as a consequence heat up. Since this happens even with no load or input, I think it is something related to the schematic or layout. I am working on the review now. 

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    TI__Mastermind 19880 points

    Hi James, 

    As we have moved this debug to email I will go ahead and move this thread to closed. Slight smile

    Regards,
    Sydney Northcutt