My design is to use UCD9244 + 2 UCD7242s to generate 1.5V and 1.8V for 2 66AK2H14 SOCs. The details can be seen in the second page in the attached file. UCD9244_UCD74120_UCD7242.pdf
The Fusion design configuration file is here.V7_K2_UCD9244 .xml
You could see there are beads between UCD7242's output power rail and the SOC's power pin. And the part name of these beads is Murata BLM21PG220SN1 22ohm@100MHz 6000mA 0805.
The problem I met is,
1. If I do not mount NB21, NB22, R187, R173 but mount R334, R335, the 1.8V generated by UCD7242 will be stable.
2. If I mount NB21, NB22, R187, R173 but do not mount R334, R335, the SOC1_VCC1V8 should be unstable and SOC1_VCC1V8 is just 0.87V without no PWM inputs to its own UCD7242 channel.
In situation 2, the waveform of SOC1_VCC1V8 is
And its PWM is
And SOC2_VCC1V8 has voltage value of 0.87V and no PWM.
So can anyone give me some hints to debug further?