This anomaly applies to Revision 3, build codes QFAA-Exx, QCAA-Exx, CAAA-Exx.
The LFCLK RC oscillator frequency can have a frequency error of up to -25 to +40% after reset. A +/- 2% error is stated in the Product Specification.
Always.
The LFCLK RC oscillator frequency is inaccurate.
Calibrate the LFCLK RC oscillator before its first use after a reset.