Figure 15. Capacitance change versus DC bias voltage
5.2.2 Inductor selection
The chosen DC-DC inductor can be particularly important. Many applications can have several different parameters to consider.
These parameters can include size, composition, price, or emission level to name a few. The table below presents the minimum
electrical characteristics for the inductor to meet the data sheet ratings. Note that your application may require inductors that
exceed these characteristics for a variety of reasons.
Table 1. Electrical characteristics for the DC-DC inductor
Inductor size
10 µH
Only recommend the nominal value 10 uH, +-20% tolerance
Inductor current rating*
120 mA
Buck mode
Inductor current rating*
320 mA
Boost mode vdd1p8 supplying 1.8 V
Inductor current rating*
400 mA
Boost mode, vdd1p8 supplying 3.3 V
Inductor DC resistance (ESR)
0.2 Ω
For boost mode, it is needed a <0.2 Ω inductor
0.5 Ω
For buck mode to achieve better efficiency it is recommend <0.2 Ω
*Current rated as saturation current (Isat)
For the DC-DC inductor’s ESR, it is estimated that the addition of each 0.1 Ω causes 1~2 percent efficiency lost. This resistance
includes inductor’s ESR, PCB trace and component leads. Higher values than 0.5 Ω, may cause instability, especially with low
VDCDC_IN voltage. Below are some recommended inductors.
NXP Semiconductors
Hardware design Guidelines
MKW4xZ/3xZ/3xA/2xZ DC-DC Power Management, Rev. 3, 04 June 2021
Application Note
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