PF3000 LICELL pin connection options

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PF3000 LICELL pin connection options

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yevgeniy_maksim
Contributor I

I find the following passage in the PF3000 Rev. 9 datasheet:

6.3.11.3 Coin cell battery backup

The LICELL pin provides for a connection of a coin cell backup battery or a “super” capacitor. If the voltage at VIN goes below the VIN threshold (VTL1), contact-bounced, or removed, the coin cell maintained logic is powered by the voltage applied to LICELL. The supply for internal logic and the VSNVS rail switches over to the LICELL pin when VIN goes below VTL1, even in the absence of a voltage at the LICELL pin, resulting in clearing of memory and turning off VSNVS. Applications concerned about this behavior can tie the LICELL pin to any system voltage between 1.8 V and 3.0 V. A 0.47 μF capacitor should be placed from LICELL to ground under all circumstances.

In the case where I don’t have a back-up battery connected to LICELL and I am concerned about the state of VSNVS when Vin < UVDET, what are my option?

  1. Can I apply 1.8V-3.0V generated by the PMIC to LICELL pin or the voltage source needs to be external?
  2. Do I need to disable the coin cell charger (Register COINCTL – ADDR 0x1A)?

Thank you,

Yevgeniy

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reyes
NXP TechSupport
NXP TechSupport

Hi Yevgeniy,

 

Yes, you can apply 1.8V-3.0V generated by the PMIC to LICELL pin, however, if VIN pin is lower than VTL1, then the regulators of the PMIC will turn off and therefore LICELL will not be powered causing loss of voltage of VSNVS and cleaning the memory.

It is recommended to supply LICELL to an external ‘always on’ regulated voltage source (between 1.8 V and 3.0 V).

 

Yes, 0x1A if no rechargeable coin cell is attached LILCELL pin, you should disable the coin cell charger  using Register COINCTL – ADDR 0x1A by setting COINCHEN bit to ‘0’.

 

Regards,

Jose

NXP Semiconductors

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reyes
NXP TechSupport
NXP TechSupport

Hi Yevgeniy,

 

Yes, you can apply 1.8V-3.0V generated by the PMIC to LICELL pin, however, if VIN pin is lower than VTL1, then the regulators of the PMIC will turn off and therefore LICELL will not be powered causing loss of voltage of VSNVS and cleaning the memory.

It is recommended to supply LICELL to an external ‘always on’ regulated voltage source (between 1.8 V and 3.0 V).

 

Yes, 0x1A if no rechargeable coin cell is attached LILCELL pin, you should disable the coin cell charger  using Register COINCTL – ADDR 0x1A by setting COINCHEN bit to ‘0’.

 

Regards,

Jose

NXP Semiconductors

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yevgeniy_maksim
Contributor I

Hello Jose,

Thank you for the response.  Just as a follow up question...With the COINCHEN bit set to '0', do I need some sort of current limiting resistor between the 1.8V rail and the LICELL pin or straight connection is fine?  Without knowing exactly what is happening with each power supply inside of the part, I probably don't want to end up back-powering any of them.

Thanks,

Yevgeniy

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reyes
NXP TechSupport
NXP TechSupport

Hi Yevgeniy,

 

You can go with a straight connection.

 

Regards,

Jose

NXP Semiconductors

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