HOLTEK BS814A-1

The BS81x is a family of 2–16 key touch devices that detect human contact via external touch pads. The high level of integration allows applications to be implemented with a minimal number of external components. BS81x series devices are equipped with serial or parallel interfaces for convenient communication with an external MCU, enabling device configuration and touch pin monitoring. Special internal circuitry ensures excellent power supply noise rejection, reducing the likelihood of false detections and improving reliability in touch switch applications under harsh environmental conditions. With features such as auto-calibration, low standby current, and excellent voltage fluctuation immunity, this series of touch key devices provides a simple and effective solution for implementing touch key operation across a wide range of applications. The series delivers simple and reliable touch switch functionality for applications requiring 2–16 touch keys, with a complete touch key implementation requiring very few external components. In addition to simple parallel output, a two-wire serial interface and binary output are also available for convenient communication with an external MCU. Sensitivity adjustment is straightforward — simply connecting a small capacitor to the touch key input pin allows different sensitivity levels to be set by varying the capacitance value. With fully integrated adaptive voltage drop functionality, the LDO typically required in touch switch applications can be eliminated. The device series offers two operating modes: normal mode and standby mode. If no touch key action is detected within 8 seconds of power-up, the device automatically enters standby mode to reduce power consumption. When a key is pressed, the device wakes up and enters normal mode, outputting the key status until all keys are released, after which the system returns to standby mode after another 8 seconds. The BS8112A-3 and BS8116A-3 support individual wake-up key configuration. Output characteristics vary by model: all output pins of the BS812A-1, BS813A-1, and BS814A-1 use an NMOS structure with internal pull-up resistors, requiring no external resistors — the output is logic high when no touch is detected and goes low on the corresponding output when a touch is detected. The BS816A-1 offers a CMOS output type in addition to the NMOS output type, with logic low output when no touch is detected and the corresponding output going high when a touch is detected. The BS814A-2 and BS818A-2 are equipped with a serial interface for convenient connection to an external host MCU. When the device detects a touch key press, it drives the data pin low, which can be used to wake up the host MCU. Upon receiving the low level, the host MCU can send a clock signal to the clock pin and read back the key status from the data pin. Most features are shared across the BS81x series: the BS8112A-3 and BS8116A-3 provide I2C functionality, allowing certain options and sensitivity settings to be configured via the I2C interface; the BS814A-2 and BS818A-2 include a serial interface; the BS812A-1, BS813A-1, BS814A-1, and BS816A-1 feature parallel output; and the BS816A-1 and BS818A-2 include two hardware options to enhance application flexibility.

• Operating voltage: 2.2V~5.5V
• Low standby current
• Auto-calibration
• Reliable touch detection
• Standby and normal operating modes
• Maximum key-press duration detection
• Adaptive voltage drop function
• Level hold support with selectable active-low or active-high output
• NMOS output with internal pull-up / direct CMOS output
• Serial interface and parallel output support
• Sensitivity adjustable via external capacitor
• Minimal external components required