nRF54L15 high power consumption when VDD is less than ~2.29V

RE: nRF54L15 high power consumption when VDD is less than ~2.29V

Kazi Afroza Sultana — Fri, 24 Apr 2026 09:32:24 GMT

Hello,

I agree with you. We should explain this in the datasheet not to confuse the reader.

For now, CAPACITANCE value is the load capacitance CL from the crystal datasheet.

I have talked to team about this. Hopefully there will be an updated version of this chapter on upcoming version.

Thanks.

Kazi

RE: nRF54L15 high power consumption when VDD is less than ~2.29V

cyber_v1 — Fri, 10 Apr 2026 12:02:26 GMT

Kazi,

We verified it and it seems CAPACITANCE in the formula is the capacitance the crystal must see. After changing it from 17000 to 9000 it works! Around 8uA with barebones k_sleep(FOREVER)!

I'd say the documentation is quite confusing; it shows how CL is calculated, and then goes on about the configuration of the internal capacitors, and under the formula: "CAPACITANCE is the desired capacitor value in pF". So one might think the CAPACITANCE is Cᴵᴺᵀ, but it's CL? Could you please confirm?

(The documentation of the load-capacitance-femtofarad in nordic,nrf-lfxo could also be improved)

Thank you for your help!

RE: nRF54L15 high power consumption when VDD is less than ~2.29V

Kazi Afroza Sultana — Fri, 10 Apr 2026 05:02:35 GMT

Hello,

The load frequency of the crystal oscillator you are using is 9pF. Its in the require ranged according to product specification.

nRF54L15 supports internal capacitors for the LFXO. If the chip has internal capacitors, following formula is used for calculating INTCAP register.

INTCAP = round( (2*CAPACITANCE - 12) * (FICR->XOSC32KTRIM.SLOPE + 0.765625 * 512)/512 + FICR->XOSC32KTRIM.OFFSET/64 )

Can you try to check that INTCAP register is correctly calculated for your crystal's 9 pF load capacitance?

RE: nRF54L15 high power consumption when VDD is less than ~2.29V

cyber_v1 — Wed, 08 Apr 2026 12:20:26 GMT

Additionally, can Nordic provide the oscillation loop maximum critical transconductance parameter for HFXO and LFXO in the nRF54 family?

RE: nRF54L15 high power consumption when VDD is less than ~2.29V

cyber_v1 — Tue, 07 Apr 2026 12:55:38 GMT

It seems the reason for the increased power consumption is the low frequency crystal oscillator not starting up at lower supply voltages.

Are there any special requirements for LFXO not listed in the documentation? I've noticed there is a section about choosing the right HFXO but not about LFXO.

We're using the SC-20S 32.768kHz 20PPM 9pF oscillator from Seiko.