Why is the waveform of VSNVS different?

[tomo]

Hello all,

I verifying my designed custom board that has a i.MX 6DualPlus and MMPF0100F9ANES.
I noticed the VSNVS ramp waveform is different when I checked the power up sequence.
Why is the waveform of VSNVS different?
Please refer attached file for more detail.

Regards,
tomo

[igorpadykov · Accepted solution]

Hi Tomokazu

reason is that vsnvs behaviour is different when applying voltage first time and described in

sect.6.4.7VSNVS LDO/Switch MMPF0100 Datasheet :

The default setting of the VSNVSVOLT[2:0] is 110, or 3.0 V, unless programmed otherwise in OTP. However, when the coin cell is applied for the very first time, VSNVS will output 1.0 V. Only when VIN is applied thereafter will VSNVS transition to its default, or programmed value..

http://www.nxp.com/docs/en/data-sheet/MMPF0100.pdf

Best regards
igor
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[tomo]

Hi,igorpadykov

Thank you for your reply.

In my custom board, the LICELL pin has an one capacitor (0.1uF), and there is no coin cell.

VSNVS voltage is seem to be approximately 0.35V when second start Vin input, but VSNVS will not start from 1.0V.

Is this case, do you think does the PMIC recognition that the coin cell has been removed?

[igorpadykov]

Hi Tomokazu

yes without coin cell VSNVS will not start from 1.0V.

Best regards
igor

[tomo]

Hi igorpadykov

Thank you for your reply.

Sorry, I'm confusing.

I found this sentence "However, when the coin cell is applied for the very first time, VSNVS outputs 1.0 V" in Datasheet.

- I understand that behaivior when coin cell exist in the circuit.(Start from 1.0V)
- I understand your answer when coin cell NOT exist in the circuit. (Not start from 1.0V)

My custom board has not coin cell, but the first time will starting from 1.0V.

Best regards,

[igorpadykov]

Hi Tomokazu

snvs timings are described on Figure 6. Default Start-up Sequence MMPF0100 Datasheet

http://www.nxp.com/docs/en/data-sheet/MMPF0100.pdf

if you are using for i.MX 6DualPlus NXP Sabre SDB schematic as reference, there should

be no issue with snvs if installed D10 on p.2 SPF-28857 schematic

Schematics
Design files, including hardware schematics, Gerbers, and OrCAD files
for i.MX 6QuadPlus (i.MX 6DualPlus emulation) (REV 1)

i.MX 6QuadPlus SABRE Development Board|NXP 

Best regards
igor