CXHA31134 and CXHA31135 are integrated circuit chips designed specifically for capacitive touch button applications. Both have built-in multi-channel 10 bit ADC processing units, supporting automatic calibration and high-precision signal processing, and only require minimal external components to achieve stable and reliable touch detection. CXHA31134 supports up to 28 touch channels and is packaged in QFN40; CXHA31135 supports up to 36 channels and is packaged in QFN48. Both support I ² C communication interface, suitable for efficient data exchange with the main control MCU.
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[ CXHA31134 ]"
In modern human-computer interaction devices, touch control technology is widely used in fields such as home appliances, consumer electronics, and industrial control due to its intuitive, flexible, and durable characteristics. CXHA31134 and CXHA31135, as two high-performance single-chip capacitive touch control ICs, are ideal choices for touch button applications due to their high integration, low power consumption, and multi-channel support. This article will delve into the characteristics, functions, applications, and technical details of these two chips, providing comprehensive references for engineers and developers.
1、 Product Overview
CXHA31134 and CXHA31135 are integrated circuit chips designed specifically for capacitive touch button applications. Both have built-in multi-channel 10 bit ADC processing units, supporting automatic calibration and high-precision signal processing, and only require minimal external components to achieve stable and reliable touch detection. CXHA31134 supports up to 28 touch channels and is packaged in QFN40; CXHA31135 supports up to 36 channels and is packaged in QFN48. Both support I² C communication interface, suitable for efficient data exchange with the main control MCU.
2、 Main functional features
2.1. Automatic calibration functionThe chip automatically initializes and obtains benchmark values after power on, and undergoes regular automatic calibration in subsequent work to adapt to environmental changes and improve detection stability.
2.2. Multi channel supportCXHA31134 supports 28 sensor channels, while CXHA31135 supports 36 channels, which can be flexibly configured as touch buttons or capacitive detection channels.
2.3. High precision ADC and filteringBuilt in 10 bit SAR ADC and low-pass filter effectively suppress noise and improve signal-to-noise ratio.
2.4. Wide voltage operating rangeSupports 2.8V to 3.6V power supply, with an I/O voltage range of 1.8V to 3.6V, suitable for various power environments.
2.5. Low power designUnder normal operating mode, the typical power consumption is only 2.5mA, suitable for battery powered devices.
2.6. Industrial temperature rangeThe working temperature ranges from -20 ℃ to+85 ℃, meeting the application requirements in harsh environments.
3、 Internal structure and pin function
The chip integrates AFE (Analog Front End), digital processor, 32K Flash memory, power management module, and 48MHz oscillator internally. The pins are divided into power class (VDD, VSS), sensor channel (S1– S36), communication interface (SCL, SDA, INT), and control pin (RSTN). Unused sensor channels need to be suspended to avoid interference.
3.1. Internal Structure Diagram
3.2. Pin arrangement
3.3. Pin Function
4、 Electrical characteristics and switch characteristics
4.1. Power Supply VoltageThe recommended working voltage is 2.8V; 3.6V， The maximum voltage is -0.3V to+3.6V.
4.2. I/O levelHigh level is 0.7× IOVCC， Low level is 0.3× IOVCC。
4.3. Clock frequencyThe typical value of the internal oscillator is 48MHz, I² The C clock supports up to 400kHz.
4.4. Boost outputThe internal LDO charge pump can output 5V voltage (VDD5) for driving high-voltage sensors.
4.5. Chip Parameters
4.5.1) Electrical characteristics
4.5.2) Switch characteristics
4.6. Working conditions
4.6.1 Extreme working conditions
(1) If the chip operates for a long time under the above extreme parameter conditions, it may cause a decrease in device reliability or permanent damage
When any parameter reaches or exceeds these limit values in actual use.
(2) All voltage values are tested relative to the system ground.
4.6.2 Recommended working conditions
5 I² C communication interface
The chip supports I² In slave mode, the device addresses are 0x70 (write) and 0x71 (read). The data transmission format complies with standard I² C protocol, supports multi byte continuous reading. The INT pin pulls down when a touch is detected, notifying the host to read the status register.
6、 Application design suggestions
6.1. Touchpad DesignIt is recommended to use a circular touchpad with a diameter of 12mm and parallel CT capacitors (0– 25pF) to optimize sensitivity.
6.2 PCB layoutWhen the touchpad is directly arranged on the PCB, it is recommended to cover it with a 2mm acrylic board to enhance the touch experience.
6.3. Power filteringEach power pin (VDDA, VDDD, VDD5) needs to be connected to a 1μ F capacitor to ground to ensure stable power supply.
6.4 ESD ProtectionThe chip is an electrostatic sensitive device and requires anti-static measures to avoid ESD damage during soldering or operation.
6.5. Application Information
6.5.1) CXHA31134 Application Diagram
6.5.2) CXHA31135 Application Diagram
7、 Program flowchart
The main control MCU interacts with the chip through the following process:
7.1. Initialize I² C interface;
7.2. Pull down the RSTN pin to reset;
7.3. Delay for 1 second and wait for the chip to start;
7.4. Check the status of the INT pin, and if it is low, read the touch status register;
7.5. Through I² C continuously reads 4 bytes (CXHA31134) or 5 bytes (CXHA31135) of data to obtain the touch status of each channel.
8、 Encapsulation information
8.1. CXHA31134 adopts QFN40 packaging, with a size of 5.0mm× 5.0mm；
8.2. CXHA31135 adopts QFN48 packaging, with a size of 6.0mm× 6.0mm；
8.3. There are heat dissipation pads at the bottom of the package, and it is recommended to fully connect them with the PCB ground layer to improve heat dissipation performance.
9、 Function Description
The CXHA31134/CXHA31135 touch button chip provides a simple and reliable way to meet the needs of 28 touch buttons/36 touch buttons
Only a few external components are needed to implement touch button applications, while providing IIC communication interface output for convenient communication with external MCUs..
9.1 Channel selection
CXHA31134 provides up to 28 touch button channels, while CXHA31135 provides up to 36 touch button channels. CXHA31134/CXHA31135 can be selected
Any channel can be used as a touch button channel (connected to a touchpad or CT capacitor), and the remaining unused channels only need to be suspended. for better
To obtain the benchmark value, it is recommended that the touchpad size should be the same, and unused channels must be suspended.
Note: The recommended size for the connected touchpad is a circular diameter of 12mm. The range of CT capacitors connected in parallel with the touch channel is 0-25pf.
9.2. Maximum button duration
To minimize unintentional key detection such as accidentally touching the sensing electrode, the chip has set a maximum key duration function internally
Yes, when a touch button is pressed, the internal timer starts counting. Once the button is pressed for too long, exceeding about 1 minute, the touch
The chip will ignore the touched state, recalibrate, obtain a new reference value, and reset the output state to initialization.
9.3. Automatic calibration function
After power on, the chip will initialize and obtain the first benchmark value. If the button is not pressed continuously, the touch chip will remain pressed for a fixed period of time
After the cycle expires, the benchmark value will be automatically calibrated so that it can dynamically change according to the external environment.
9.4 Button Touch
When the chip detects a touch action, it will pull down the INT pin to notify the MCU to read the touch status information. After all touch buttons are released, INT will be set high.
If the touchpad is directly arranged on the PCB board, it is recommended to cover it with a 2mm acrylic board for better touch effect.
9.5. Touch Status Register
Register Description: The touch status register stores the touch status of touch buttons. CXHA31134 has 28 touch channels, while CXHA31135 has
36 touch channels. Support multiple channels being touched simultaneously, with each bit of the touch status register corresponding to the status of each KEY, 0: no touch,
1: There is touch. When there is a touch, the INT pin is pulled low, and the host can read the value of the touch status register. After the touch is released, the INT pin returns to high level.
CXHA31134 requires 4 bytes to store touch status information, while CXHA31135 requires 5 bytes to store touch status information. The MCU reads it through the IIC interface
Touch status information can continuously read multiple bytes of data, and the touch status register address automatically increments.
tenSummary
CXHA31134 and CXHA31135 provide efficient and reliable solutions for touch button applications with their high integration, low power consumption, multi-channel support, and stable automatic calibration capabilities. Whether it's home appliance panels, industrial controllers, or smart devices, these two chips can significantly enhance the interactive experience and reliability of products. Developers can choose suitable models based on specific channel requirements and quickly implement productized applications by combining the design suggestions provided in this article.
Ten Related Products
| sensor | |||||
| model | detection method | detection distance | Output configuration | Drive Type | remark |
| CXHA31125 | Light blocking groove type | 5mm (slot width) | The light blocking indicator can be turned on through the portLConnect to（+）When selecting transparency, the indicator light is on | NPN | photoelectric sensor |
| CXHA31125A | Light blocking groove type | 5mm (slot width) | The light blocking indicator can be turned on by connecting port L (+) to select the light transmitting indicator | NPN | photoelectric sensor |
| CXHA31125B | Light blocking groove type | 5mm (slot width) | The light blocking indicator can be turned on by connecting port L (+) to select the light transmitting indicator | NPN | photoelectric sensor |
| model | Working Voltage | Port withstand voltage | PWM cycle | package form | |
| CXHA31126 | 2.4V-5V | 6V | 6.13ms | SOT23-5 | vibration sensor |
| CXHA31127 | 2.4V-5V | 6V | 4.87ms | SOT23-5 | vibration sensor |
| CXHA31128 | 2.8V-9.5V | - | - | SOP8/SOT23-6 | vibration sensor |
| CXHA31129 | 2.7V-5.2V | - | Adjustable duty cycle | SOT23-6/DFN6H | vibration sensor |
| CXHA31130 | 2.7V-5.2V | - | Frequency adjustable | SOT23-6/DFN6H | vibration sensor |
| CXHA31131 | 2.7V-5.2V | - | I2C control | MSOP10/SSOP10/QFN3*3 | vibration sensor |
| model | Working Voltage | Number of interfaces | Number of driving buttons | package form | |
| CXHA31132 | 2.2V-5.5V | twoThefour | eight | SOP16 | Touch sensor |
| CXHA31132S | 2.2V-5.5V | two | 8 (Supports slider function) | SOP16 | Touch sensor |
| CXHA31133 | 2.2V-5.5V | two | eight | SOP16 | Touch sensor |
| CXHA31134 | 2.8V-3.6V | four | twenty-eight | QFN40 | Touch sensor |
| CXHA31135 | 2.8V-3.6V | four | thirty-six | QFN48 | Touch sensor |
