CXHA31132 is a highly integrated capacitive touch sensing chip that supports up to 8 touch button inputs. The chip integrates efficient signal processing circuits and automatic calibration algorithms internally, which can effectively suppress the impact of power fluctuations and environmental changes on touch detection, providing stable and reliable touch response. Its wide voltage operating range (2.2V-5.5V) and ultra-low standby current (as low as 12 μ A) make it highly suitable for battery powered or low-power devices.
-
[ CXHA31132 ]"
With the rapid development of smart home appliances, industrial control, and consumer electronics, touch sensing technology has gradually replaced traditional mechanical buttons and become the mainstream choice for human-computer interaction due to its beauty, durability, and ease of cleaning. CXHA31132 is a high-performance 8-channel capacitive touch button control chip with high sensitivity, low power consumption, strong anti-interference, and rich output interfaces, which can be widely used in various scenarios that require touch control.
One Product Overview
CXHA31132 is a highly integrated capacitive touch sensing chip that supports up to 8 touch button inputs. The chip integrates efficient signal processing circuits and automatic calibration algorithms internally, which can effectively suppress the impact of power fluctuations and environmental changes on touch detection, providing stable and reliable touch response. Its wide voltage operating range (2.2V– 5.5V) and ultra-low standby current (as low as 12μ A) make it highly suitable for battery powered or low-power devices.
2、 Main characteristics
2.1. Multi channel touch inputSupports 8 independent touch buttons.
2.2. Automatic calibration functionThe system automatically tracks environmental changes, dynamically adjusts benchmark values, and avoids false triggering.
2.3. Dual output modeAutomatically switch between standby/working mode, supporting 2-wire serial interface and 4-wire binary parallel interface, making it easy to interface with external MCUs.
2.4. Adjustable sensitivityEach touch channel can flexibly adjust sensitivity through an external capacitor (0– 25pF).
2.5. Voltage fluctuation resistanceEquipped with anti voltage fluctuation function, built-in voltage fluctuation suppression function, no need for external LDO, reducing costs.
2.6. Low power designSupports both normal and ultra-low power modes, with standby current as low as 12μ A.
2.7. Maximum Key Time LimitMaximum key output time detection, built-in 64 second timeout protection to prevent long press misoperation.
2.8. Packaging Form：SOP16， Suitable for high-density PCB layout with minimal peripheral components.
2.9. Built in pull-up resistor/CMOS direct output, supports serial and parallel output, and external capacitor adjusts sensitivity
3、 Electrical characteristics and performance parameters
3.1 CXHA31132 performs excellently under recommended working conditions:
3.1.1) Power supply voltage: 2.2V -5.5V
3.1.2) Standby current: 12μ A (ultra-low power mode)
3.1.3) Working current: 1.2mA @ 3V, 2.2mA @ 5V
3.1.4) Response time: 100ms (standby mode), 100ns (working mode)
3.1.5: Output driving capability: 4mA (NMOS current), 20mA (CMOS source current)
Its wide temperature range (-40 ℃ to+85 ℃) and excellent ESD protection capability make it suitable for industrial applications in harsh environments.
3.2. Extreme working conditions
(1) Long term operation of chips under the above extreme parameter conditions may result in reduced device reliability or permanent damage. It is not recommended to have any parameter reach or exceed these limit values during actual use.
(2) All voltage values are tested relative to the system ground
4、 Function Explanation
4.1. Output Mode Selection (OMS)
Output interface type can be selected through OMS pin:
4.1.1) Suspended: 2-wire serial interface (Clock+Data)
4.1.2) Grounding: 4-wire binary parallel output (BIN0– BIN3)
The chip has two working modes, standby mode and working mode. If no buttons are touched within 8 seconds after the system is powered on, it will automatically enter standby mode to reduce power consumption. Once any key is touched, the CXHA31132 chip can be awakened, enter working mode, and output key status. When all keys are not pressed, it will enter standby mode again after 8 seconds.
4.2. Power Mode Selection (LSC)
The LSC pin is used to switch power consumption modes:
4.2. 1) Suspended: Normal mode, fast response speed
4.2.2) Grounding: Ultra low power consumption mode, slightly increased wake-up time (0.5– 1 second)
4.3. Automatic calibration and anti-interference
The chip has automatic calibration function, which can dynamically adjust the reference value and adapt to environmental changes. Its built-in anti voltage fluctuation function can effectively prevent false triggering caused by power supply jitter and improve system stability.
After power on, the chip will initialize and obtain the first reference value. If no button is pressed within 1 second in normal mode or 32 seconds in standby mode, the touch chip will automatically calibrate the reference value after a fixed time period, so that the reference value can dynamically change according to the external environment.
4.3.2) Sensitivity adjustment;
Adjusting the sensitivity of touch buttons according to user needs is a very important consideration in most applications. Sensitivity can be adjusted by changing the size and floor area of the PCB electrodes (directly below the electrodes), or by changing the thickness of the insulation material. At the same time, CXHA31132 provides a way to adjust different sensitivity requirements by adding capacitors to the touch input pins.
4.4. Sensitivity adjustment
Users can adjust sensitivity by paralleling a capacitor (Ct) on the touch pin, and the larger the capacitor value, the lower the sensitivity. Supports external capacitor adjustment from 0pF to 25pF.
4.5. communication interface
4.5.1）Serial modeOutput 16 bit data frame, including key status, checksum, and stop bit, supporting host wake-up function. The chip is equipped with a serial interface that allows for simple communication with external devices. When the touch chip detects that the touch key is pressed, it will output a low level on the Data pin to wake up the host. After receiving the low level, the host will input a clock signal through the Clock pin and read back the key value from the Data pin. When the Clock pin inputs a low level, the touch chip prepares data, and after the Clock pin sends a high level, the host reads data from the Data line. Read data in groups of 8 clock signals each time. You can also directly read the key value through polling without waiting for the Start bit. When there is a data reading error, it takes about 6ms to read again.
When the Clock pin receives a clock signal, the touch chip will generate a 16 bit data byte and remove it from the Data pin. Among them, Bit11-Bit8 generate checksum to represent the total number of touched keys. For example, the checksum is“ 0010” This means that two keys have been touched. As for which button was touched, you can check the status of Bit7 to Bit0 bits. Bit7 to Bit0 are used to indicate whether the corresponding touch keys Key8 to Key1 have been touched. If it is 0, it indicates that the corresponding key has been touched, and if it is 1, it indicates that the corresponding key has not been touched. Start bit: When the button state changes, the Data pin outputs a low potential to wake up the host, and the host reads the key value.
Bit0: Key1 status (0=touched, 1=not touched);
Bit1: Key2 status (0=touched, 1=not touched);
Bit2: Key3 status (0=touched, 1=not touched);
Bit3: Key4 status (0=touched, 1=not touched);
Bit4: Key5 status (0=touched, 1=not touched);
Bit5: Key6 status (0=touched, 1=not touched);
Bit6: Key7 status (0=touched, 1=not touched);
Bit7: Key8 status (0=touched, 1=not touched);
Bit11～8：校验和 --“0”的总数，即被触摸按键的总数。
Bit15~Bit12: Stop bit, always“ 1010B”
4.5.2) Parallel ModeDirectly output 4-digit binary code, representing the currently pressed key number, with fast response speed.
CXHA31132 also provides the function of parallel interface, allowing key value transfer with external devices. When selecting the parallel interface as the output type, the touch key value can only reflect one key and cannot reflect multiple keys at the same time. When there is no touch key pressed, BIN3-BIN0 are all high level. When any key is pressed, BIN3 is low level and can be used to wake up the host. BIN2-BIN0 represent the pressed key value,
As shown in the table below:
4.6. Function Description
The CXHA31132 touch button chip provides a simple and reliable way to meet the need for 8 touch buttons. Touch key applications can be implemented with minimal external components, while providing 2-wire serial interface and binary parallel interface outputs for convenient communication with external MCUs.
Easy sensitivity adjustment, simply add a capacitor to the touch input pin to adjust different sensitivities. The built-in anti voltage fluctuation function can save the cost of an LDO (voltage regulator module).
CXHA31132 offers 2 options to increase application flexibility
4.7. Maximum button duration;
To minimize unintentional key detection such as accidentally touching the sensing electrode, the chip is equipped with a maximum key duration function internally. When a touch button is pressed, the internal timer starts counting. Once the button is pressed for too long, exceeding about 64 seconds, the touch chip will ignore the state of the touched button, recalibrate, obtain a new reference value, and reset the output state to the initial state.
5、 Application design suggestions
5.1. Typical Application Circuit
5.1.1) Serial mode: Clock and Data lines are recommended to be connected to 10kΩ Pull up the resistor and add a filtering capacitor if necessary.
5.1.2 Parallel Mode: BIN0‐ BIN3 is directly connected to MCU GPIO and can also serve as an interrupt wake-up signal.
5.1.3) Power filtering: It is recommended to parallel a 0.1 μ F capacitor between VDD and GND, and place it as close to the chip as possible.
5.1.4) Internal structure diagram
5.2. PCB layout precautions
5.2.1) The touch electrode should be kept away from high-frequency signals and power lines to reduce interference.
5.2.2) The electrode size and covering material affect sensitivity and need to be adjusted according to actual applications.
5.2.3) Unused Key pins should be grounded to avoid introducing noise due to suspension.
5.3. Software design suggestions
5.3.1) It is recommended to use polling or interrupt to read key values to avoid long-term blocking.
5.3.2) In serial mode, if there is a read error, a delay of 6ms should be applied before attempting again.
5.3.3) The automatic calibration and timeout functions can be utilized to enhance the user experience.
6、 Packaging and mechanical characteristics
CXHA31132 adopts standard SOP16 packaging, with small size and reasonable pin spacing, suitable for automated surface mount production. The packaging structure is sturdy, with good thermal performance, and meets industrial grade reliability requirements.
Conclusion
CXHA31132 is a comprehensive and stable capacitive touch button chip that combines high sensitivity, low power consumption, and strong anti-interference ability. Its flexible output interface and automatic calibration mechanism make it very suitable for touch application design in fields such as smart homes, industrial control, consumer electronics, and medical devices. Whether it's simple single key control or complex multi key interaction systems, CXHA31132 can provide reliable and efficient solutions.
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 |
