Coin Cell Confusion

[atillametetured]

Hello,

I am a bit confused about the power map of the Sabre Board with PF0100 and would be thankful if someone could clear it up for me. So there is a LICELL charger in PF0100 that can charge an external Li+ battery. When Vin is gone, the regulator VSNVS takes over the battery control and outputs a voltage at VSNVS according to user settings. However (this is where I need help with), this scenario cannot power the system, that is, rest of the regulators will not function during Coin Cell operation and only the LDO SNVS will supply the SNVS along with power on SNVS_IO.

On the other hand, if I go with the battery charger circuit described in Sabre Smart Devices schematic, can I eliminate the need for the other coin cell? I think then, it is a matter of how long you want to keep SNVS powered, but you get the risk of depleting your mains batteries and not having any battery power left for the SNVS.

What you guys think? For a battery operated system, is 3 Li+ (2 for main supply and 1 for SNVS) the way to go?

Thanks in advance and sorry for the long post.

Best Regards,

Mete

[art · Accepted solution]

The VDD_SNVS_IN power rail of the processor supplies so-called Secure Non-Volatile Storage (SNVS) module that contains a secure real time counter, a monotonic counter, a general purpose register, and some tamper detection and power control logic. This module can remain functional when only the VDD_SNVS_IN voltage is applied and all other processor power is not. So, the only purpose of a coin cell battery in a system is to provide the power to the SNVS block (if required) when main power is off and main power supply is disconnected.

Have a great day,
Artur

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[atillametetured]

Hi Artur,

That helps. Thanks for the information.

Regards,

Mete