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TPA2008D2: About the short circuit protection circuit of TPA2008D2

user1018920
Prodigy 10 points
Part Number: TPA2008D2

The datasheet says that this device has a built-in "short circuit protection circuit".
Please teach us about this function.

In the description of the datasheet
・When a short circuit is detected in the output, the shutter down mode is set.
・Shutdown mode can be canceled by changing the SHUTDOWN pin from low to high, or by turning the electric power from OFF to ON.
-If the short circuit is not released, it will be shut down again.
It has been described as.


The current circuit "SHUTDOWN pin is fixed high".
In this state
(1)When the output (ROUTP and ROUTN) is short-circuited
"Short circuit detection-> shutdown mode-> shutdown mode cancellation-> short circuit detection ..."
Will short circuit detection and shutdown mode be repeated?
Or is it still in shutdown mode because the "SHUTDOWN pin change from low to high" is not detected?
* The power remains ON.

(2) When ROUTP and ROUTN are short-circuited and the shutdown mode is set, is it okay to recognize that the output of the L side output (LOUTR, LOUT) is also stopped?

(3) In the case of "short circuit detection and shutdown mode are repeated", is there any effect on the device (heat generation, damage in some cases, ignition, etc.)?

(4) When a signal is input to the signal pins (LIN, RIN) in shutdown mode, is there any effect on the device?

(5) The R side output (ROUTP and ROUTN) is short-circuited, but the speaker connected to the L side is producing sound.
It seems that the short circuit protection is not working, but is there any effect on the device when using it in this state?
* The R side input (RINN) is a variable resistor with no input signal (input voltage 0V).
It is unconfirmed whether the input voltage is completely 0V.
Or is it just not noticed because the short circuit protection function is working but the "short circuit detection and shutdown mode" repeats quickly?
For the circuit, refer to "Figure 17" on page 15 of the data sheet.
* Since the speaker is connected to an 8Ω product,
"L1, L2 = 33uH, C1 = 0.47uF, C2, C3 = 0.1uF"
It is supposed to be.


I think the questions are duplicated, but thank you.

  • 0
    TI__Guru* 98255 points

    Hi,

    I think I'm not understanding your questions completely, but let me add some comments on the protection scheme of these kind of devices:

    • The short circuit protection of this device is a latch type. This means that when the device detects the short, it will shutdown the amplifier, it will not try to enable back again by itself. Either SHUTDOWN or power (PVDD) must be toggled to take the device back to active after a short circuit is detected.
    • There is no affect on the device if you have input signal while it is in shutdown more or unpowered.
    • Since there is only one shutdown control signal for both channels, I think the short circuit protection would shutdown both channels of the amplifier, eg. if it detects short on R channel it will shutdown both channels.

    If you have any further questions please let me know. If you have any non-related questions you can always post a new thread.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0
    Prodigy 10 points

    Ivan Thank you for your answer.

    -It turned out that the short-circuit protection of this device is a latch type.
    -It was found that if a short circuit is detected, it can be recovered by SHUTDOWN or power OFF → ON.
    -It was found that there is no influence of the device when there is an input signal in the shutdown state.
    -It was found that when a short circuit on one side channel was detected, both channels shut down.

    What about the first inquiry (5)?
    -----------------
    The R side output (ROUTP and ROUTN) is short-circuited, but the speaker connected to the L side is producing sound.
    It seems that the short circuit protection is not working, but is there any effect on the device when using it in this state?
    * The R side input (RINN) is a variable resistor with no input signal (input voltage 0V).
    It is unconfirmed whether the input voltage is completely 0V.
    For the circuit, refer to "Figure 17" on page 15 of the data sheet.
    * Since the speaker is connected to an 8Ω product,
    "L1, L2 = 33uH, C1 = 0.47uF, C2, C3 = 0.1uF"
    It is supposed to be.
    -----------------

    Paradoxically, is it okay to recognize that there is no problem because a short circuit has not been detected?
    (I'm not sure why it doesn't detect a short circuit.)

  • 0 in reply to user1018920
    TI__Guru* 98255 points

    Hi,

    On question 5, do you mean there is short on R channel, but L channels is still active?
    If my assumption is correct, have you verified this? As explained in my previous reply, I would expect both channels to shutdown if a short circuit is detected on either of the channels.

    If you have a short on R channel, but don't have any signal at the input, and the device is not detecting the short on R channel, it is most likely because the short circuit detection scheme inside the device is working based on the current at the output driver, if there is no signal on the shorted channel, there will be minimal or no current flowing through the "shorted" output.
    Operating in this state would be risky as any change at the input signal of the "shorted" channel could cause the short circuit protection to trigger. If using the device in this situation I would suggest to AC couple to GND the unused channel, although operation is still not guaranteed in this use-case.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • +1
    Prodigy 10 points

    Ivan Thank you for your answer.

    It is said that there is a risk in operating in the state like (5). What kind of risk is there?
    If it was operated in the state of (5), is there a possibility that the device will be damaged (further burning)?

  • 0 in reply to user1018920
    TI__Guru* 98255 points

    Hi,

    • As mentioned, the risk would be that the unused channel can trigger a short circuit detection.
    • No expected damage or burning, the only risk is a short circuit detection, which will shutdown the device.

    Best regards,
    -Ivan Salazar
    Applications Engineer