1. Description before product rectification:
The product is two separate Bluetooth headsets, the two headphones are connected wirelessly, and then the left ear is connected to the playback device via Bluetooth. When conducting the ESD test of ±4KV, it is found that the Bluetooth headset will restart, or cannot connect to the Bluetooth state, which does not meet the standard B class of IEC61000-4-2, the following figure is the test point (due to the problem of product confidentiality, the original picture is not convenient to provide):
Second, the product rectification process:
The red icon in the picture above is an electrostatic test point, because these are two bare metal dots, one of which is GND and the other is 5V, and after repeated tests, it has been confirmed that this product will appeal when ± 3KV. Disassemble the product, observe its internal structure, and find that under these two test points is the Bluetooth antenna, the antenna and the PCB board are connected by electric shock, so first we take out the antenna, and when testing, we find that the product has improved (can hit about 3.5KV). To confirm that the antenna has a certain interference with ESD, we connect an ASIM ESD in parallel to the ground on the antenna (model: ESD5D003TA, the junction capacitance of this ESD is 0.3pF has no effect on the performance of the antenna), and then when testing, it is found that the product can accept the electrostatic test of 3.5KV; but it is still unstable at 4KV.
Therefore, in the processing of the ESD test point, ASIM ESD (model: ESD5D150TA) is connected in parallel to ground at 5V and a magnetic bead is strung on 5V and a large capacitor is connected in parallel to ground. When testing, it was found that the product can accept ±4KV ESD test, which is in line with the IEC61000-4-2 class B standard, and it was recently confirmed that the product accepts ±5KV ESD test.
III. Summary:
The cause of ESD interference is not only related to the PCB board, but also has a lot to do with the structure of the product, when carrying out ESD rectification, we must first find out which module the product is disturbed, and the right medicine is a shortcut to ESD rectification.
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