MMPF0100F0EP SW1A/B buck converter output Issue

[vinodkumar]

Hi,

     We used MMPF0100F0EP PMIC for our design.

     we referred Sabre SD board for our design.

     I have attached schematic.

     As per MMPF0100F0EP datasheet, SW1A/B output should be 1.375V. But we are getting only 0.04V.(In SW1C, output is proper 1.375V. )

     In Vgen4 LDO output, we supposed to get 1.8V but we are getting 2.176V.

     other output levels are normal.

     please guide us.

[vinodkumar]

I am not using that interfaces.

so i dont want

[tamilarasane]

n Imx6 Quad , after pressing RESET switch SOM doesn't boot again. it boots only after hard power on/off.

As per my understanding, through external reset released, internal Reset will release only after  VDD_ARM_CAP and VDD_SOC_CAP supplies
are stable (internal  LDO_CORE and LDO_SOC).

so , i doubt these internal voltage domains and their input voltages  VCC_SW1AB_CORE and VCC_SW1C_SOC of PMIC (MMPF0100F0AEP)

Findings:

1. in Linux, boots  after reset  switch is pressed with out problem and  VCC_SW1AB_CORE and VCC_SW1C_SOC voltages of  PMIC are fine. ( no voltage dip occurs-here current consumption from  VCC_SW1AB_CORE is  < 500mA)

2. In android
         1. if reset switch is pressed at the time of uboot, and kernel loading , booting occurs without problem ( up to this process current consumption form VCC_SW1AB_CORE is  < 700mA )
         2. once android application launches , current consumption from VCC_SW1AB_CORE is increased >900mA, and voltages dip occurs ( snap shot attached) if reset switch is pressed now,  doesn't boot again.


3. first dip occurs from 1.35 to 1.28V at that time current is around 700mA.  if i press reset switch here, boot occurs without problem

4. After some time (  launching android application) continuous dip occurs  from ( 1.28V to 0.992V) here current is around 900mA  . if i reset here, board doesn't boot . andVCC_SW1AB_CORE is in 0.992V itself.

Green -VCC_SW1AB_CORE of PMIC
Blue- VCC_SW1C_SOC of PMIC

Same issues occurs in 3 boards.

Is anyone faced this issue...? Pls let me know the solution for this.?

Thanks

Tamilarasan.

[vinodkumar]

Hi Loic,

               We are getting correct output voltage of 1.8V at VGEN4 when it is isolated from load.

               It is giving output of 2.8V when it is connected load.

               1.8V loads are processor power supply pins of NVCC_LCD, NVCC_CSI & NVCC_ENET.

               We are assuming that processor is loading this VGEN4 part into 2.8V

               Please suggest.

[loichureau]

Hi Vinod,

Yes this is strange, are you sure that it's not 3.3V needed for NVCC_LCD, CSI and ENET ?

Regards,

Loic

[JorgeRama_rezRi]

Hi Vinod,

The portion of the schematics you attached looks good.

- Is it possible for you to disconnect all loads from SW1 and VGEN4 and measure the voltages with the outputs open?

- How many boards do you have and have tested? What's the failure rate?
- Is the issue happening at boot, at run mode or both?

- What's the PF0100 internal registers configuration for default voltages and for run mode setting for these regulators?

Best regards.

Jorge.

[vinodkumar]

Hi Jorge,

     We have disconnected load  & tested with No load condition.

     SW1A/B @ No load & SW1C @ No Load --> SW1A/B O/P Voltage 3.34V & SW1C O/P Voltage 1.374V

     SW1A/B @ No load & SW1C @ Load --> SW1A/B O/P Voltage 3.34V & SW1C O/P Voltage 1.374V  

     SW1A/B @ load & SW1C @ No Load --> SW1A/B O/P Voltage 0.894V & SW1C O/P Voltage 1.374V

     SW1A/B @ load & SW1C @ Load --> SW1A/B O/P Voltage 0.0V & SW1C O/P Voltage 1.374V

     We have Assembled two boards. In Board 2, some assembly issue is there.

     This issue is happening at Power up time.(We haven't boot)

     We haven't given any connectivity to PMIC i2c Lines.

     PMIC MMPF0100F0EP is factory programmed device. It has power sequence.(Please see attached). is it really need to check internal registors?

[reyes]

Hi Vinod Kumar,

You should not have any problem to start-up if the MMPF0100 is properly pre-programmed (you can check the register only to check if was properly factory programmed, but you don’t really need to check them), just please confirm that you are connecting VDDOTP pin to GND.

Have you tested it with a different MMPOF0100 soldered to your board, just to check if this particular device is damaged?

I have another inquiry, are you using MMPF0100F0EP or MMPF0100F0AEP version of the device?

I ask you this because you mentioned that you are using MMPF0100F0EP, which is not the latest revision of the silicon (MMPF0100F0AEP is the latest revision of the silicon) and might have some issues on the start-up of the regulators as mentioned in ER19 in the errata document (http://cache.freescale.com/files/analog/doc/errata/MMPF0100ER.pdf) so, if you are not using the latest revision of the device, I would recommend you to use the workaround mentioned in the errata.

I know that errata is not giving any details about Single phase SW1A/B problems, but, since I’m not very sure of what could be causing this issue, only as a suggestion, I direct you to the errata so you can implement the workaround mentioned for ER19 where it’s mentioned that it could have a “False start and/or non-start of regulators”, which, could be related to your issue, or probably not, but it’s just a suggestion.

Have a great day,
Jose Reyes

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

[vinodkumar]

Hi all,

     Thank you for your suggestion.

     It is assembly problem. we have changed inductor & working fine.

[loichureau]

Hi Vinod,

Issue with VGEN4 output voltage is also corrected ?

Best Regards,

Loic