Determining initial transmission phase offset in an NFC device

A device configured to operate in NFC card mode only, the device comprising:

• a matching circuit;
• and
• an NFC chip coupled to the matching circuit, the NCF chip comprising:
• an internal oscillator;
• a non-volatile memory storing correction data indicative of a frequency offset of the internal oscillator relative to a nominal oscillator frequency;
• and
• an NFC processing unit,
• wherein the NFC processing unit is configured to:
• determine an initial RF matching resonance frequency of the NFC device utilizing the internal oscillator;
• read correction data from the non-volatile memory;
• determine a corrected RF matching resonance frequency of the NFC device based on the initial RF matching resonance frequency and the correction data;
• and
• determine an initial transmission phase offset based on the corrected RF matching resonance frequency.

A method of manufacturing an NFC device configured to operate in NFC card mode only, the method comprising:

• manufacturing an NFC chip, the NFC chip comprising an internal oscillator, a non-volatile memory, and an NFC processing unit;
• determining, during a silicon production test procedure, correction data indicative of a frequency offset of the internal oscillator relative to a nominal oscillator frequency;
• writing the determined correction data into the non-volatile memory;
• mounting the NFC chip in the NFC device and connecting the NFC chip to a matching circuit;
• determining an initial RF matching resonance frequency of the NFC device utilizing the internal oscillator of the NFC chip;
• reading the correction data from the non-volatile memory of the NFC chip;
• determining a corrected RF matching resonance frequency of the NFC device based on the initial RF matching resonance frequency and the correction data;
• and
• determining the initial transmission phase offset based on the corrected RF matching resonance frequency.