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TPA3221: TPA3221-Out Cap Issue

Part Number: TPA3221

The terminal customer of Guangwo feedback the following problems when using TPA3321:

1. When the output of 4PCS bootstrap capacitor C5/C6/C30/C31 value is 333, the test finds that when the sound is turned to the maximum and ,TPA3221 will be triggered protection when the low-frequency signal IC of 100HZ is played (even if it is not connected to load), but the signal of 1KHZ does not show the above phenomenon

2. If the output capacitor is changed to 105, the above phenomenon will disappear. The customer wants to confirm whether such modification will affect the reliability of the overall scheme, please help to confirm.

3.Below shows the schematic,pls help to check it.


  • Hi Ning.

    According to your description, the protection triggered should be fake OC. The OC protection detection of our device is to sample the voltage across the MOS when it is turned on, and then divide it by RDS(on) to obtain the current flowing through the MOS. If the capacitance of the BST capacitor is not large enough, the MOS will not be fully turned on, resulting in a large voltage across the measured MOS triggering a false OC.

    Increasing the BST capacitor is a correct solution, but an excessively large BST capacitor will affect the startup of the device. The specific and appropriate capacitance value needs to be adjusted according to your actual application scenario.


    Wei Qiu.

  • Hi Weiqiu,

    Thanks for your support,I will talk with customer.Then feedback to you.