Three important factors to consider when selecting SMD inductors

The main specifications of inductance include, in addition to size, the inductance value at switching frequency, DC impedance (DCR) of the coil, rated saturation current, rated rms current, AC impedance (ESR), and Q factor. Depending on the application, the choice of inductance type - shielded or unshielded - is also important

Similar to DC bias in capacitors, manufacturer A's 2.2 μ The inductance of H may be different from that of manufacturer B. The relationship between the inductance value of the SMD inductor and the DC current within the relevant temperature range is an important curve that needs to be obtained from the manufacturer. On this curve, it can be found that the rated saturation current (ISAT) is generally defined as the DC current when the inductance value drops to 30% of the rated value. Some inductance manufacturers do not have ISAT regulations. They may have provided a DC current at a temperature 40 ℃ above the ambient temperature

When the switching frequency exceeds 2MHz, special attention should be paid to the AC loss of the inductor. The ISAT and DCR of inductors from different manufacturers listed in the specification manual may have different AC impedances at the switching frequency, resulting in different efficiency differences under light loads. This is crucial for improving the battery life of portable power systems, as the system spends most of its time in sleep, standby, or low-power mode

As SMD inductor manufacturers rarely provide ESR and Q factor information, designers should proactively request it from them. The relationship between inductance and current provided by manufacturers is often limited to 25 ℃, so relevant data within the operating temperature range should be requested. The bad situation is usually 85 ℃