4. Effect of noise suppression measures
Verifying the noise suppression effect of common mode choke coils
In order to evaluate the noise suppression effect of a common mode choke coil, we ran a CAN FD transceiver with a signal generator and observed the common mode noise of the CAN-H and CAN-L lines with a spectrum analyzer. We inserted three types of common mode choke coils and verified the effects of each.
We can see that the noise level increases with the increase in the signal generator bit rate.
Moreover, of the three types of common mode choke coils, the DLW32SH101XF2 was observed to have a comparatively higher noise suppression effect. The DLW32SH101XF2 is able to effectively suppress the noise at every bit rate.
Verifying the effect of conducted emission suppression measures
Next, we verified the noise suppression effect of the DLW32SH101XF2 with a conducted emission measurement (150 Ω method).
This measurement complies with the "Emission of RF Disturbances" defined under IEC 62228-2:2019.
By using the DLW32SH101XF2, we were able to satisfy the most stringent Class III limit for conducted emissions.
Verifying the immunity improvement effect
To continue, we conducted a DPI (Direct Power Injection) test, which is one type of immunity test, to verify the immunity improvement effect. This measurement complies with the "Immunity to RF Disturbances" defined under IEC 62228-3:2019.
By using the DLW32SH101XF2 in the DPI test as well, we were able to satisfy the most stringent Class III limit value.
- Common mode noise is often a problem in CAN FD
- A common mode choke coil can effectively remove the common mode noise
- The mode conversion characteristics of the common mode choke coil are also important to prevent common mode noise from occurring due to mode conversion
- The DLW32SH101XF2 is effective for both conducted emission suppression and immunity improvement.
Our recommended common mode choke coil