TL084A: Charger Ipeak誤觸發原因分析

已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

您好，

     与抗外部噪声相关的主要因素是EMIRR、CMRR和PSRR。

     在相关TL084ACDR替换TL084AIDT案例的讨论中，客户正在调查系统布线配置可能引起的干扰问题。

     作为短期解决方案，类似您的应用仍使用共模电感来滤除电气噪声干扰。

您好，

目前我們正在評估以 TL084ACDR 替換原先使用的 TL084AIDT。由於兩者在 CMRR 規格上相近，理論上應可有效濾除共模雜訊干擾；此外，電路中已使用匹配電阻，因此由偏移電流所造成的偏移電壓誤差預期應該相當小。

然而，目前對於 EMIRR（Electromagnetic Interference Rejection Ratio） 的相關規格與評估基準仍不太清楚，且部分 Datasheet 並未列出 EMIRR 參數。

目前我們的改善方向是透過在訊號路徑中加入電感Core，以抑制可能的共模或差模雜訊。不過仍想進一步確認，是否還有其他未注意到的關鍵參數，可能導致干擾問題。

若有相關建議或建議優先關注的規格項目，敬請協助提供意見，謝謝。

您好，

目前我們正在評估以 TL084ACDR 替換原先使用的 TL084AIDT。由於兩者在 CMRR 規格上相近，理論上應可有效濾除共模雜訊干擾；此外，電路中已使用匹配電阻，因此由偏移電流所造成的偏移電壓誤差預期應該相當小。

然而，目前對於 EMIRR（Electromagnetic Interference Rejection Ratio） 的相關規格與評估基準仍不太清楚，且部分 Datasheet 並未列出 EMIRR 參數。

目前我們的改善方向是透過在訊號路徑中加入電感（Ferrite Core），以抑制可能的共模或差模雜訊。不過仍想進一步確認，是否還有其他未注意到的關鍵參數，可能導致的干擾問題。

若有相關建議或建議優先關注的規格項目，敬請協助提供意見，謝謝。

您好，

     和产品线专家咨询了一下，Brian Wang也咨询过您这个问题，请问是代替贵司提问的吗？

     产品线专家回复如下，请参考：     

• The main factors that relate to immunity to extrinsic noise are EMIRR, CMRR, and PSRR.
• The OPA4188 has exceptionally good EMIRR, CMRR, and PSRR.  It also has very good intrinsic noise.  It will be challenging to find a device with better than OPA4188 for both intrinsic noise and extrinsic noise rejection. 
  • Some potential alternatives are OPA4192, OPA4205.  These are other high end op amps with good CMRR, PSRR, EMIRR, and intrinsic noise.  These devices are similar to OPA4188 but not chopper amplifiers.  It is possible chopping noise is impacting your result so maybe one of these devices would be a better choice.
• One other possibility is that it is not a noise pickup but is ADC settling.  However, if the issue was ADC settling, I would not expect adding a ferrite bead would help.  The fact that the ferrite bead helped does make me think it is extrinsic noise.
• One other possibility is that the circuit is not stable and the noise is a low level oscillation.  This seems unlikely as I don’t see anything in the schematic that looks questionable from a stability perspective.  Also, the captured results from the customer show that the noise is fairly low in amplitude (only a few codes), and typically stability will look like a more significant issue.
• I think it would be useful to import the ADC data into the analog calculator tool as I mentioned in the last email.  This will let us know if the noise is extrinsic, or extrinsic by showing the noise spectrum.  Also, a full schematic with the ADC and all values will help.

Brian Wang回复如下：
Update the status from RDs. Due to the extended and multiple busbar cable runs connecting various power boards to the control board in this 150MW UPS system, the R&D is currently investigating potential interference issues caused by the system wiring configuration.

To narrow down the scope of this issue, R&D has been requested to conduct an ABA swap experiment to reproduce and verify the problem systematically between ST and TI parts.

As a short term solution now, the common mode chokes (as shown in the previously provided images) are being implemented to filter out electrical noise interference.

如果不是代替贵公司提问的，请提供在问题发生时输入和输出电压的示波器图或图片，我们可以尝试进一步提供帮助。

我们确实在数据手册中测量了EMIRR，如图5-36所示，但ST芯片没有测量，因此无法进行比较。