Electronic – How to choose the appropiate analog power supply filter inductor

circuit-designinductorpowerschematics

I'm currently studying designs for a pulse oximeter for use with Arduino, I have seen two Schematic designs form the same company, https://www.protocentral.com/sensors/1113-protocentral-afe4490-pulse-oximeter-shield-for-arduino-v2-642078949425.html and https://www.protocentral.com/open-source-health/1252-healthypi-v3-basic-hat-kit-for-raspberry-pi.html . Both of them are identical and are base around the AFE4490RHAT IC from Texas Instruments. Both designs have 4 inductors : L1, L2, L3 , L4.

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1) What are these inductors used for in the design?

2) In one of the designs they are using 4 CIG22L100MNE and in the other 4 LPS3010 (they don't specify the full part number) but the Samsung one seems to be discontinued and the other one seems to be not recommended for new designs, I'm trying to choose and equivalent I have compared the specifications between the two parts and a part from the inductance they seem to have very different properties regarding current rating, DC resistance and inductance frequency, what specifications are more important when choosing a replacement part?

Best Answer

1) The inductors are used to filter noise from supply voltage. As each supply node has its own inductor, noise caused by periodic gulping of current on one supply node cannot pass on to other supply nodes and cause problems taking the sensitive measurements.

2) That is a good question and there may not be an answer. It seems that the evaluation kit for the pulseoximeter chip used a 10uH inductor LPS3010-103MLB everywhere, most likely to reduce cost by using same part for everything, and that reference design got copied everywhere. So as long as the parameters are reasonably same almost any inductor could be used.