Stmicroelectronics Asia Pacific Pte Limited

Stmicroelectronics (grenoble 2) Sas

Stmicroelectronics S.a.

Hugo Gicquel

Leonard Liviu Dinu

Marc Sabut

Abhishek Singh

Fabien Reaute

Yannick Guedon

Roger Petigny

Sophie Minot

Chee Weng Cheong

Lionel Vogt

Christophe Forel

François Van Zanten

Eng Jye Ng

Li Cai

Supriya Raveendra Hegde

Jean-Luc Moro

EngJye Ng

Beatrice Lafiandra

Fouad Bissane

A touch screen controller includes an input stage configured to receive and condition a touch output from a touch matrix to produce a touch signal. An accumulation stage is configured to receive the touch signal and accumulate the touch signal to produce an accumulated output. The accumulated output is digitized by an analog to digital converter to produce a touch strength value. A given amount of charge is subtracted from or added to accumulated output during a next accumulation if the touch strength value is greater than an upper threshold or less than a lower threshold. This avoids saturation of components in the touch screen controller and therefore increases the signal to noise ratio.

Oversampled high signal to noise ratio analog front end for touch screen controllers

Disclosed herein is a circuit including a driver circuit applying a received drive signal to a capacitive sensing line of a capacitive touch panel as a boosted drive signal, the driver circuit powered by a boosted supply voltage. A charge pump circuit receives an input supply voltage and output the boosted supply voltage, the charge pump circuit including a voltage sensing circuit to sense the boosted supply voltage and a comparison circuit to compare the sensed boosted supply voltage to a threshold and produce a comparison signal. A control circuit determines a ratio of a pulse width of the comparison signal to the drive signal, and tunes operation of the charge pump circuit to drive the ratio to match a performance threshold.

Auto-tunable drive system for high efficiency synchronized charge pump for use with touch screen system

A touch screen controller disclosed herein includes a circuit configured to generate a digital touch voltage comprises of samples, at a base sampling rate. The touch screen controller also includes a digital processing unit configured to analyze a first subset of samples of the digital touch voltage samples to determine noise content thereof, the first subset of samples corresponding to samples at a first investigated sampling rate that is a first function of the base sampling rate. The digital processing unit is also configured to analyze a second subset of samples of the digital touch voltage to determine noise content thereof, with the second subset of samples corresponding to samples at a second investigated sampling rate that is a second function of the base sampling rate, and determine a preferred sampling rate from among the first and second investigated sampling rates as a function of determined noise content thereof.

Parallel analysis of different sampling rates in a touch screen controller

A feedback stage for an integrator circuit is provided. The integrator receives a first input current and a second input current that include respective measurement current components and an offset current component. The integrator integrates the first input current and the second input current and generates a first output voltage and a second output voltage. The feedback stage including a transconductance amplifier detects a difference between the first output voltage and the second output voltage and sinks or sources a first output current and a second output current based on the difference between the first output voltage and the second output voltage. The first output current is additively combined with the first input current and the second output current is additively combined with the second input current to mitigate the offset current component at an input of the integrator.

Auto zero offset current mitigation at an integrator input

An electronic device includes a plurality of charge-to-current converters each including a first NMOS transistor having a source coupled to a sense line, a first capacitor between a gate and source of the first NMOS transistor so that a transient component of noise from the sense line is applied to both, a first PMOS transistor having a source coupled to the sense line, a second capacitor between a gate and source of the first PMOS transistor so the transient component of the noise is applied to both, a first current mirror having an input coupled to a drain of the first NMOS transistor and an output coupled to an output for that charge to current converter, and a second current mirror having an input coupled to a drain of the first PMOS transistor and an output coupled to the output for that charge to current converter.

Concurrent sensing in touch screen controller with improved noise rejection

Disclosed herein is a touch screen controller including a driver circuit applying a drive signal to a drive line of a capacitive touch sensing panel. The driver circuit is powered by an accurate supply voltage. A driver supply circuit receives an input supply voltage and outputs the accurate supply voltage. The driver supply circuit includes a clocked comparator comparing a divided version of the accurate supply voltage to a reference voltage and outputting a comparison signal based thereupon. A voltage control circuit (e.g. a charge pump circuit) generates the accurate supply voltage in response to the comparison signal. The clocked comparator and voltage control circuit are both clocked by a driver supply circuit clock.

Highly accurate synchronized charge pump for capacitive touch screen system

An oscillator circuit includes a first current generator circuit that generates a current complementary to absolute temperature and a second current generator that generates a current proportional to absolute temperature. A temperature slope control circuit adjusts slopes of the current complementary to absolute temperature and the current proportional to absolute temperature in a complementary fashion and adds the current complementary to absolute temperature to the current proportional to absolute temperature after slope control to produce a temperature independent current. A current control circuit adjusts magnitude of the temperature independent current to produce a magnitude adjusted temperature independent current. A current controlled oscillator generates an output signal as a function of the magnitude adjusted temperature independent current.

Temperature stable oscillator

A method of differential self-capacitance measurement is used to enhance a signal-to-noise ratio of sense lines in a touch panel display, thereby improving touch sensor accuracy. The differential self-capacitance measurement is implemented for a touch panel using charge sharing between adjacent sense lines of the touch panel matrix. Sequential differential self-capacitance measurements can be compared with one another by computing the difference |C&#x2212;C|&#x2212;|C&#x2212;C| to sense a change caused by an intervening event. By scanning the entire touch panel matrix, events can be tracked across the touch panel.

Self-sensing touch panel

Disclosed herein is an electronic device including a sensing layer including a plurality of sense lines, and a plurality of single ended charge converter circuits each receiving input from a corresponding one of the plurality of sense lines. The electronic device also includes a plurality of current mirror circuits, each respectively mirroring output from one of the plurality of single ended charge converter circuits so as to produce two substantially identical outputs for each of the plurality of single ended charge converter circuits. There may be a plurality of subtractor circuits coupled to the plurality of current mirror circuits, with each of the plurality of subtractor circuits configured to output a voltage that is a function of a difference between outputs from two of the plurality of current mirror circuits associated with adjacent ones of the sense lines.

An alternating current (AC) drive signal having a first frequency and a high logic level at a boosted supply voltage is applied to drive a capacitive sensing line of a capacitive touch panel. The boosted supply voltage is generated by boosting an input voltage. The voltage boosting is effectuate by a charge pump circuit operating synchronous to assertion of the AC drive signal with a charge transfer time that is adaptable to different capacitive load conditions.

Highly efficient charge pump synchronized to the drive signal of a touch screen system

A circuit described herein includes a charge to voltage converter circuit having an input coupled to receive a sense signal from a sense node associated with a mutual capacitance to be sensed, and an output. A reset switch is coupled between the output of the charge to voltage converter circuit and the input of the charge to voltage converter. An accumulator circuit is configured to accumulate voltages at the output of the charge to voltage converter circuit and to generate an accumulator output signal. Control circuitry is configured to generate control signals for the reset switch and accumulator circuit so as to reduce noise in the accumulator output signal.

Sampling frequency and accumulator sweeping in a touch screen controller

Disclosed herein is an electronic device including a display layer generating display noise based on scanning thereof and a sensing layer including a plurality of sense lines. The display noise is capacitively coupled from the display layer to each of the plurality of sense lines of the sensing layer. A differential charge converter circuit has first and second differential inputs respectively coupled to corresponding ones of the plurality of sense lines, and first and second reference inputs. The first and second reference inputs of the differential charge converter circuit are coupled to voltage references during a reset period, and are decoupled from the voltage references during a scan period.

Differential sensing in touch screen controller with improved noise rejection

An activity detector for a differential signal formed by two components may include a current source connected to a power supply line, and a first transistor has a drain being powered by the current source, and has a source that forms a first input terminal receiving a first component of the differential signal. A second transistor has a drain being powered by the current source, and has a source forms a second input terminal receiving the second component of the differential signal. A bias circuit applies a potential to the gates of the first and second transistors, establishing a balance condition where all the current from the current source is distributed between the two transistors when the first and second input terminal potential is equal to a threshold value. An activity indication terminal is taken from the drains of the first and second transistors.

Growing community of inventors

Grenoble, France

Hugo Gicquel