Successive approximation analog-to-digital converter

Analog-to-digital converter comprising:

• an input terminal receiving a voltage to be converted, the voltage to be converted being comprised in a conversion range bounded by a first voltage and a second voltage,
• an amplifier having a first input terminal and an output terminal forming an analog output terminal of the converter,
• a first switch connecting the input terminal of the amplifier and the output terminal of the amplifier,
• first, second, third and fourth connections connected in parallel to the input terminal of the amplifier, each connection respectively comprising first, second, third and fourth capacitors having a first terminal connected to the first input terminal of the amplifier,
• a second switch connecting a second terminal of the first capacitor to the output terminal of the amplifier,
• a first comparator receiving the voltage to be converted and at least one first comparison voltage and configured to perform comparison between the voltage to be converted and the at least one first comparison voltage, and to deliver, on a first digital output, a first digital value on at least a first bit representative of said comparison,
• a second comparator receiving a first intermediate voltage and at least a second comparison voltage and configured to perform comparison between the first intermediate voltage and the at least one second comparison voltage, and to deliver, on a second digital output, a second digital value on at least a second bit representative of said comparison,
• a voltage source configured to:
• apply the voltage to be converted on a second terminal of the first, second, third and fourth capacitors during a first period,
• apply a first reference voltage on the second terminal of the second capacitor during a second and third periods, the first reference voltage being representative of the first digital value,
• apply the first reference voltage on the second terminal of the third capacitor during the third period,
• apply a second reference voltage on the second terminal of the fourth capacitor during the third period, the second reference voltage being representative of the second digital value,
• a control circuit configured to calculate, by means of the amplifier and the second switch,
• the first intermediate voltage from the voltage to be converted, from the first digital value and from said first voltage and second voltage,
• a second intermediate voltage from the voltage to be converted, from the first and second digital values and from said first voltage and second voltage.

Operating method of an analog-to-digital converter comprising:

• providing an analog-to-digital converter comprising
• an amplifier having a first input terminal and an output terminal forming an analog output terminal of the converter,
• a first switch connecting the input terminal of the amplifier and the output terminal of the amplifier,
• first, second, third and fourth connections connected in parallel to the input terminal of the amplifier, each connection respectively comprising first, second, third and fourth capacitors having a first terminal connected to the first input terminal of the amplifier,
• sampling a voltage to be converted during a first period by applying said voltage to be converted to second terminals of the first, second, third and fourth capacitors, the voltage to be converted being comprised in a conversion range bounded by a first voltage and second voltage, the amplifier being connected as a follower by means of the first switch,
• comparing the voltage to be converted with a first comparison voltage by means of a first comparator and delivering a first digital value on at least a first bit,
• applying a first reference voltage on the second terminal of the second capacitor, during a second period, the first reference voltage being representative of the first digital value,
• calculating a first intermediate voltage by means of the amplifier and the first and second capacitors, from the voltage to be converted and the first reference voltage,
• comparing the first intermediate voltage with a second comparison voltage by means of a second comparator and delivering a second digital value on at least a second bit,
• during a third period, applying the first reference voltage on the second electrode of the third capacitor and applying a second reference voltage on the second terminal of the fourth capacitor, the second reference voltage being representative of the second digital value,
• calculating a second intermediate voltage by means of the amplifier and the first, second, third and fourth capacitors, from the voltage to be converted, the first reference voltage and the second reference voltage.