Hello,
I have an application using the DA14585 that is subject to extreme EMI. I believe that this is disturbing the high frequency oscillator and causing the microcontroller to not run or constantly reset in situations. Would it be possible to replace the 16MHz crystal with a MEMS oscillator to improve this?
数据表仅列出了1和1.2V的最小和典型的外部时钟电压，但没有最大电压。Would this oscillator work?
谢谢！
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嗨ahiggs，
感谢您的问题和您对我们的BLE解决方案的兴趣。让我检查一下，我会回复你。
谢谢，PM_Dialog
嗨ahiggs，
Although there are a some drawbacks using an external oscillator (e.g. power consumption, phase noise, cost, ..), the DA14585 can handle an external 16MHz clock. The output voltage of the oscillator should be divided to 1.2V.
On the other hand, if EMI is the issue here, wouldn't some kind of shielding do a better job?
谢谢，PM_Dialog
Hi, thanks for the response. We are already using PCB mount shielding, but the environment is harsh enough for this to not be sufficient. I can upload an image of the PCB where you can see the mounts for the shielding and general layout if anything looks off if this would help.
嗨ahiggs，
Yes, please upload an image of your PCB. It would be helpful.
谢谢，PM_Dialog
Hi,
这是布局的PDF。该器件由小型3.6V可再充电电池供电，用于使用极端EMI测量高压环境中的热电偶。
嗨ahiggs，
We have the layout reviewed and the grounding of the xtal is looking unusual. We combine the ground ring around the xtal with the top layer ground. So we don't have the space marked with the green arrows – see attached.
谢谢，PM_Dialog
Hello,
当我遇到的建议和反对接地圈时，我已经使用地面设计进行了测试。我们没有注意到两者之间的恶劣环境中的性能差异。
您是否有建议与未使用的GPIO和LFXTAL引脚有关？
谢谢，
Ansel
嗨ahiggs，
Could you please answer on our questions below?
所有GPIOS的默认设置都是输入下拉。仅在本申请中使用p0_0。其他GPIO或LF XTAL没有痕迹。我们会说这是不太可能的，那些针对这个问题有助于这个问题。
Is this your final layout? If not, then please upload your final layout with the exact information when it is ready.
谢谢，PM_Dialog
我不知道振荡器会导致问题。在14585上运行的代码基于DSP示例并定期上示例ADC（通过Easy_Timer）并通知接收器以值，它在该项目和其他项目上进行了很好的测试，并且从未遇到过问题。（在5中进一步回答）
2.This crystal。16MHz，18pf，80ohm，30ppm。已在其他14585个设计上使用（标准工业环境）
3. That the shielding does not cover the trace to the antenna? I did not think that this was necessary as it is closely protected by the ground plane.
4.该DESGN用于靠近发射器和接收器的实验室测试，并且不需要卓越的性能来保证阻抗控制或测量的成本。
5. This board works in a non-EMI environment and with moderate EMI present. The amplifier connected to P0_0 measures a differential thermocouple signal with a rapidly changing common-mode voltage. When the CMV changes between 0 and 10kV, the 14585 functions as expected and is connectable and outputs correct data. If the CMV changes above ~10kV the 14585 will either stop advertising, advertise but not send any notifications, or advertise but immediately disconnect-reconnect-disconnect-etc from the receiver until the EMI has cleared. The CMV increases and decreases rapidly, rate of multiple kV per microsecond, and occurs at about 15Hz.
6. I do not know the exact frequency or strength. I believe it is well in the sub-GHz range but we do not have the equipment to measure it.
这是最近的布局。由于这不是串联生产的设计，我们能够相对迅速地进行更改和测试新布局。
谢谢！
Ansel
嗨ahiggs，
The 16MHz xtal does not fit to our specification.
负载电容应为10PF，80OHM ESR仅适用于频率在20MHz和29.9MHz之间的Xtals。16MHz XTAL具有150欧姆的ESR，对于我们的振荡器来说太高了。
Before trying the MEMS oscillator, changing to an xtal, that fulfills our specification would be an option.
Were you able to trim the 18pF xtal to 16MHz?
请检查AN-B-054: DA14585/586 Application Hardware Design Guidelines。
谢谢，PM_Dialog
Ok, wow, I completely overlooked that and the incorrect resistance value on Digikey also didn't help.这种晶体似乎更合适。当我们接下来修改委员会时，我会看待改变它。
I did not attempt to trim the crystal as the 14585 worked fine with it in previous designs.
谢谢！
嗨ahiggs，
我已经检查了数据表，负载电容为8pf。这应该是10pf。
谢谢，PM_Dialog
Hello,
Unless I am mistaken, the datasheet says the part numberECS-160-10-36Q-AES-TR表示此版本应该为10PF的电容。否则，阻力，分流电容和容差都在推翻范围内？
谢谢！
嗨ahiggs，
My apologies - yes the load capacitance is coded in the part number. A ECS-160-10-36Q xtal has a load capacitance of 10pF indeed.
The frequency tolerance is little big, but if you are not using it at the full temperature range and you will trimm the 16MHz oscillator. In this case the xtal will fit.
谢谢，PM_Dialog