Method of calibrating a thermometer-code SAR A/D converter and thermometer-code SAR-A/D converter implementing said method

A method of calibrating a thermometer-code successive approximation register analog-to-digital (SAR-A/D) converter comprising an Nbit-bit digital-to-analog converter (DAC) for outputting an Nbit-bit output code, the DAC comprising a first subconverter having a plurality of NTh thermometer elements Tj and a second subconverter having a plurality of NBin binary-weighted elements, the plurality of thermometer elements Tj defining the MSB bits of the Nbit-bit code and the plurality of binary-weighted elements Nbin defining the LSB bits of the Nbit-bit output code, with the Nbit-bit output code being equal to the sum of NBitTh and NBitBin where NTh=2NBitTh and NBitBin is equal to NBin=NBitBin, the method of calibrating comprising:

• determining an Integral Non-Linearity error value (εR) of an Rth thermometer-code level of the thermometer elements Tj according to the formula:
• ɛ
• R
• =
• ∑
• j
• =
• 0
• R
• -
• 1
• ⁢
• ⁢
• E
• j
• -
• R
• N
• Th
• ⁢
• ∑
• j
• =
• 0
• N
• Th
• -
• 1
• ⁢
• ⁢
• E
• j
• where:
• Ej represents relative mismatch differences between the plurality of thermometer elements Tj and a reference thermometer element Tref selected from the plurality of thermometer elements Tj of the first subconverter;
• minimizing a maximum of the error value εR to obtain a minimized error value;
• and
• generating the output code according to the minimized error.