Itoh San,
The 5MHz oscillating frequency does not cause any problem in EMI, becuase the radiation efficiency is verly by the coil, and there is no harmonics in the 5MHz waveform. There is EMI emission in the higher frequency area due to the common mode half-sine waveform, as can be seen on each of the INA, INB pin.
When local coil is used (coil located immediated near the chip), the LDC1000 sensor meets the CICPR22 EMI emission levels.
If the coil is remote, one of these must be done:
1. Use shielded cable, connect the shield to the IC side ground
2. Use a common mode choke, place it very close to the IC. Recommended CM choke: SRF3216-222Y, made by Bourns
3. Enclose the entire sensor (IC and coil) in a metal box.
Best regards,
Don Liu