Self-test method, corresponding circuit and device

A circuit configured to be coupled to a touchscreen resistive sensor that comprises a network of resistive sensor branches coupled to a number N of respective sensor nodes arranged at touch locations of the touchscreen, wherein the circuit comprises:

• a source of a reference voltage level;
• a set of switches configured to perform a test sequence by:
• i) sequentially coupling the source of the reference voltage level to the sensor nodes in the number N of sensor nodes to sequentially apply the reference voltage level thereto;
• and
• ii) jointly coupling the nodes in the number N of sensor nodes other than the sensor node in the number N of sensor nodes to a common line to which the reference voltage level is applied;
• a first comparator circuit block coupled to the common line, the first comparator circuit block configured to compare a voltage sensed at the common line with a short circuit threshold and to generate a short circuit signal indicative of a short circuit condition of the touchscreen resistive sensor as a result of the voltage sensed at the common line reaching the short circuit threshold;
• a current sensor circuit block coupled to the set of switches to sense a current level flowing at the sensor node in the number N of sensor nodes to which the reference voltage level is applied;
• and
• a second comparator circuit block coupled to the current sensor circuit block, the second comparator circuit block configured to compare an upper threshold and a lower threshold with the current level sensed at the sensor node in the number N of sensor nodes to which the reference voltage level is applied and to generate a malfunction signal indicative of malfunctioning of the resistive sensor branch coupled with the sensor node in the number N of sensor nodes to which a reference voltage level is applied as a result of the current level sensed at the sensor node in the number N of sensor nodes to which the reference voltage level is applied reaching the upper threshold or the lower threshold.

A device, comprising:

• a touchscreen resistive sensor comprising a network of resistive sensor branches coupled to a number N of respective sensor nodes arranged at touch locations of the touchscreen;
• and
• a circuit configured to generate an error signal upon determining an error condition, the circuit having a set of switches configured to perform a test sequence by:
• sequentially coupling a reference voltage to the sensor nodes in the number N of sensor nodes to sequentially apply the reference voltage thereto;
• and
• jointly coupling to a common line to the nodes in the number N of sensor nodes other than the sensor node in the number N of sensor nodes to which the reference voltage is applied.