PMIC core voltage glidches happening while booting.

[santhakumara]

Hi

I'm working iMX6 SOC based system. Below is MPN being used in the system.

SOC: MCIMX6S5DVM10AC

PMIC: MMPF0100F1AEP 

In that while loading kernel and file system crash happening randomly.

Below is the snap of power variation.

Whether it needs more decaps or any other things to be noted.

Pls suggest me what could be happening and what can be done.

regards,

santhakumar.

[reyes]

Hi,

You did not mentioned where is this “Vdd_Core_1.2V” voltage coming from, I’m assuming that it comes from the VCORE pin on the MMPF0100, please correct me if I’m wrong.

All regulators use the main bandgap as the reference. The main bandgap is bypassed with a capacitor at VCOREREF. The bandgap and the rest of the core circuitry are supplied from VCORE. The performance of the regulators is directly dependent on the performance of the bandgap. No external DC loading is allowed on VCORE, VCOREDIG, or VCOREREF.

External components required for core voltages:

A 1.0uF cap from VCOREDIG to GND.

A 1.0uF cap from VCORE to GND.

A 0.22uF cap from VCOREREF to GND.

If you need more assistance, please share your schematics.

Have a great day,
Jose

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[santhakumara]

Hi Jose,

sorry, Vdd_core_1.2V means SOC core voltage.that is VDDARM_IN

Image above also related to that only.

regards,

santhakumar.

[reyes]

Hi,

You did not sent your schematics, but I’m assuming that VDDARM_IN is supplied by VDDCORE which comes from SW1AB from the PF0100, please correct me if I’m wrong.

The recommended external components for SW1A/B output would depend on the configuration mode you are using the SW1 outputs (check Section 6.4.4.3 SW1A/B/C in the datasheet mode details about the different configuration modes), but I’m assuming that you are using “SW1A/B Single Phase” mode and for this mode, the recommended external components are:

CINSW1A (SW1A Input Capacitor): 4.7uF

CIN1AHF (SW1A Decoupling Input Capacitor): 0.1uF

CINSW1B (SW1B Input Capacitor): 4.7uF

CIN1BHF (SW1B Decoupling Input Capacitor): 0.1uF

COSW1AB (SW1A/B Output Capacitor): 2 x 22uF (you can add up to 4 x 22uF capacitors if you still having the problem you are seen).

LSW1A (SW1A Inductor): 1.0uH

* We recommend to use X5R or X7R capacitors.

Have a great day,

Jose

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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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[santhakumara]

Hi Jose,

whatever you have said is correct.

we already using decaps which is recommended.(4 22uF Decaps)

with this config only we are getting this issue.

you can see the waveform which is 1.2V while loading kernel it is comes

down to 1.05V with those glitches.

we are not using internal LDOs. thinking that 1.05V would come when

processor is in sleep mode (correct me if i'm wrong). but while kernel

loading why it has to 1.05V.

we don't think processor is loading since it is stable at 1.05V after

those glitches. ( which is shown in image ).

whether it is usually happens ??.

please suggest us what is happening and what can be done.

regards,

santhakumar.

[reyes]

Hi,

Ok, I have some extra HW related questions, but, can you send me the schematic? I would like to see the full SW1AB – VDDCORE – VDDARM_IN net connections.

Also check the VDDARM_CAP capacitors and the VDDARM_IN capacitors on the IMX6 side, these capacitor could help to reduce the ripple you are seen.

And just as a note, it is critical that the bulk and decoupling capacitors placed on the VDDARM_CAP rail be placed directly underneath the processors. Development testing has shown that proper placement of these capacitors can reduce ripple on the voltage rails by as much as 50% compared to placing capacitors outside the physical boundaries of the processor. These will result in more stable processor operations.

And just to confirm, if I understand properly, you cannot see the problem every time the kernel is loading, you can only see this issue some times. Correct?

Do you have the same issue on all of your boards?

Have a great day,

Jose