Working principle of capacitive touch chip
Time:2022-10-19
Views:1562
There is an inductive capacitance between any two conductive objects. A key, that is, a pad and the earth, can also form an inductive capacitance. When the surrounding environment remains unchanged, the inductive capacitance value is a fixed micro value. When a human finger is close to the touch button, the inductive capacitance formed by the human finger and the earth is connected in parallel with the inductive capacitance formed by the pad and the earth, which will increase the total inductive capacitance. The capacitive touch key IC will output the confirmation signal of a key being pressed after detecting that the inductive capacitance value of a key has changed. Capacitive touch keys are more sensitive to various interferences because they have no mechanical structure and all detection is a small change in electricity. Therefore, the design of touch keys, the design of touch panels and the selection of touch ICs are critical.
At present, there are two kinds of touch chips, one is resistive touch chip, the other is capacitive touch chip. Capacitive touch chip is more widely used because of its higher reliability. At present, single point touch is a common and widely used product using touch chip. With the continuous development of touch chips, various forms of touch buttons have appeared in our daily household appliances, such as the emergence of roller and slider buttons, which has enriched the application of touch chips.
Early touch chips were relatively simple and could only handle keys. With the further development of technology, the touch chip is no longer a simple key processing chip, but can now be used as a main MCU. In addition to handling touch keys, it can also handle such things as AD sampling, LED control, communication, etc. In the past, two chips, one touch chip and one main MCU, were required to realize the touch key function. Now only one touch chip is needed to solve the problem, which greatly reduces the cost of products and enables more products to use touch key technology.
Since the touch chip is integrated into MCU, the key detection becomes more flexible. Matrix scanning or AD sampling can be used, which makes the number of keys that can be identified more and more. Previously, it may require several touch chips to complete. Now a new touch chip can fully meet the requirements.
Here, I recommend the capacitive touch chip GTX314L, which is one of the green touch 3LPTM capacitive touch products. In particular, GTX314L can perform capacitance detection. There are 14 channels for green touch 3LPTM engine operation. Due to the green touch 3LPTM low-power engine, various battery powered applications can increase the service time of the product. Also based on the existing GreenTouch3TM engine technology, the reliability can guarantee the change of various noises and environments. I2C read-write interface can be used for internal control register. GTX314L can be applied to a wide range of power supply voltages from 1.8 v to 5.5 v. The CTRL pin of GTX314L provides a chip IDI2C bus that can be switched on the same chip for parallel operation of two chips.
With the advent of touch chip technology, the way of pressing keys has also changed dramatically. The key operation has become more flexible and comfortable, and the key panel has become more fashionable and beautiful. With its unique advantages, touch buttons are being used by more and more products.
With the continuous development of touch technology, the reliability and practicability of touch chip will be further improved, making the use of touch chip more extensive. At present, the integration degree of touch chip has become higher and higher. The touch chip can be used as both the main MCU and touch keys, which makes the touch chip more cost-effective and lower cost. It can be seen that the application of touch chip will be more and more extensive.
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