LDC1614: LDC1614 EMI emissions

Hello Masahiro-san,
Typically for emissions testing it is a far field emission that is being detected and our sensors are operating as a near-field resonator. The primary factors that influence far field emissions are fast voltage transients like fast rising or falling edge rates and trace lengths and wires that act like antennas at specific frequencies. Note that the worst case emissions occur when your wire lengths are approaching λ/4 to the antenna measurement frequency which creates a dipole with the measuring antenna, however you can see noticeable emissions on these tests with wire lengths as little as λ/16. So if you have a 100mm wire in your system this could effectively radiate signals as small as 187MHz. To avoid these issues you can shield the wiring with ground-shielded cable and install the capacitors to ground on either side of the wires which will shunt the higher frequency content and help provide low impedance along the wire path. The common mode choke can also help if you measure the EMI performance and need reduction at specific frequencies. Additionally, it is important to have a solid ground plane on your board and to keep power supply routing short and well decoupled to keep low impedance and minimize the distance that voltage transients have to travel. We've written an application note which discusses these and other EMI reduction techniques for LDC devices: www.ti.com/.../SNOA962
Regards,
Luke LaPointe