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Problems about UCD9244+UCD7242

Expert 2985 points
Other Parts Discussed in Thread: 66AK2H14, UCD74120, UCD7242, UCD9244

Hi all,

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?