AN-B-056 DA14680/681 Recovery from System Level ESD Events
■This document describes a method to recover the DA14680/681 from a possible system level ESD event. Such an ESD event might happen in applications using the external 32.768kHz crystal. The document presents a simple and cheap external Watchdog Circuit to Reset the DA14680/681 and recover from the event. Applications using the internal RCX oscillator and no external 32.768 KHz crystal do not require this circuitry.
●Introduction
■During non-destructive ESD testing of the final application (sytem level ESD testing) by e.g. shooting at the charger contact pins of a wearable application when the DA14680/681 SoC is in sleep mode, there is a chance the DA14680/681 does not wake up anymore by itself. When the system (application) is not recovering by itself, it is considered as a fail from a system level ESD point of view. The system level ESD test is considered as a pass when the DA14680/681 would reboot, start to advertise and can re-connect. A temporary loss of function is allowed as long as it recovers its normal operation without operator intervention. [3] [4] [5].
■When asleep, typically the DA14680/681 will keep operating at ESD contact discharge levels upto +/-4KV. At higher ESD levels, depending on the ESD protection, there is a chance the system will not wake up. This document explains a HW solution to overcome such a limitation. Since system level ESD testing is critical to a product design, we recommend customers using the DA14680/681 to implement the suggested solution in their system if an external 32.768 KHz crystal is used. Some general system level ESD protection guidelines for applications are given in [2].
■When subjected to ESD testing with the DA14680/681 in active mode does not reveal problems, the chip continues to operate up to the required ESD levels: typically +/- 6KV contact discharge.
■Applications using the internal RCX oscillator and no external 32.768 KHz crystal are expected to pass the system level ESD testing as long as the general recommendations are applied for ESD testing as indicated in [2]
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Application note & Design Guide |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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22-Feb-2022 |
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Revision 1.1 |
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AN-B-056 |
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2 MB |
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