Research On Capacitive Induction Touch Chip Applied To LED Dimming

With the continuous development of touch technology and the promotion of a series of consumer electronics manufacturers such as Apple,most of the commands issued by users in today's human-computer interaction scenarios need to be transmitted to the touch panel or touch buttons as a medium.machine.Among the wide variety of touch buttons,capacitive touch buttons have stood out because of their excellent reliability and low cost,and have achieved wide application.The Sigma-Delta modulator is the most important part of the overall capacitive touch chip design because it is not only responsible for converting the sensed capacitance value into a digital signal that is easy to process at the back end,but also directly determines the entire Capacitive touch chip performance and reliability.In the design of the modulator,the main difficulty lies in how to compromise between improving signal-to-noise ratio to improve performance and the resulting higher design complexity and potential non-ideal factors.After various trade-offs,this paper designed a capacitive sensing touch chip for LED dimming,in which the programmable gain amplifier,dual current source and sigma-delta modulator are designed.Programmable Gain Amplifier A folded cascode amplifier with differential pair input that provides a rail-to-rail input from a positive supply voltage to a negative supply voltage at low supply voltages;a dual current source structure designed to regulate critical nodes The voltage value at the capacitor C?mod,one of the current sources always keeps working,and the other is gated with the feedback signal output from the quantizer.This design reduces the pre-charging time and ensures the charging speed.The designed current is derived from the starting circuit.One drive circuit can be omitted and the circuit utilization can be improved.The current source size is extremely easy to program,and the current source can replace the external resistor to release the charge,which can reduce the bill of materials(BOM)cost;the Sigma-Delta modulator selects the second-order single-bit structure.It can meet the performance requirements,and can ensure the stability of the circuit,and the power consumption is low,the circuit structure is simple.In addition,the design of the integrator in the modulator uses Miller compensation to enhance the frequency stability,and the chopping technology can reduce the 1/f noise.This design uses the Global Foundries 0.18-?m standard CMOS process.The test results show that the sigma-delta modulator achieves a peak signal-to-noise ratio of 98 d B at a sampling frequency of 1.024 MHz and a 256-fold oversampling rate.The effective number of bits reaches 15.99 bits,and the work is performed under a 5V supply voltage.The consumption is 3.32 m W.Finally,several capacitive touch buttons are fabricated using the capacitive touch chip designed in this paper.The chip is verified by controlling the LED light switch.The experimental results show that the chip designed in this paper can realize the touch dimming function accurately and quickly.And the sensitivity is 2.12 times that of the original reference chip,and the chip cost is also reduced.