Discover Grahowlet's Touch Screen Display Monitor – Customized 5.5-inch Capacitive Solution

Technical Q & A

Q: Since the Cypress solution capacitive screen can enhance the anti-noise ability, then can we analyze the factors affecting noise from the sensor perspective?
A: The impact of the Sensor on TP performance is huge. In the capacitive touch screen module, the sensor is the sensing element, and the controller IC is the analog-to-digital converter. The sensor quality directly affects the quality of the signal received by the IC. From the structure point of view, sensor is divided into two categories, namely DITO and SITO. From the material point of view, sensor is mainly divided into two categories, namely Glass and Film. DITO uses the lower layer TX for shielding, so no shielding layer is needed. SITO's TX and RX are all on one layer, so you need a shield on the back. Technical improvements can remove the back shield. The Cypress solution uses a DITO structure with a mesh pattern to solve linearity and dangling problems. The SITO structure usually adopts a diamond pattern. This pattern has many problems, and the power supply noise is large, linearity, floating, and poor waterproof performance. The Cypress scheme uses the SITO structure plus a bee pattern to achieve the performance of the DITO structure with a mesh pattern. Because the FLASH process does not support high voltage, it can be seen that other chips in the market need high voltage when it needs to externally boost the chip. In addition to the boost, the Cypress chip adds a lot of algorithms and adopts its own patented SENSOR pattern, so in the letter The noise ratio can be done very well.

Q: About the capacitive screen we are using now, the power supply interference problem is very serious. What should we do to eliminate the interference of the power supply? Apart from scanning frequency to avoid the noise frequency of the power supply, improve the signal-to-noise ratio of the screen? Is there any other way?
A: Seeing from all current cases, power supply interference is mainly concentrated in large-size TP (7inch or above), and we have the following solutions:
(1) Choose a quality power supply. This is very important and the most effective and fundamental way to solve power disturbances;
(2) Frequency hopping. Use the spectrum analyzer to find the area where the common mode interference strength of the adapter is small, and then set the TX scan frequency to this area through software setting, which can effectively control the interference. If there is interference in the full frequency band, it is recommended to abandon the adapter;
(3) Improve the signal to noise ratio. In the initial design of TP (7.0inch or above), consider using the low-impedance surface-rent material for the RX signal channel and using the design of the double-sided trace. Try to control all the channel resistances within 10K, which can effectively control the power supply interference. ;
(4) It is also possible to change the charger, increase the algorithm filtering, and adopt Cypress, EETI, ILI schemes with strong anti-interference performance.