Date: 04/03/2011

Touch key flash MCU with 56 pixel display panel driver

Holtek has announced the release of its new Flash series MCUs with touch switch and display panel driver functions. This new series, known as the BS85xxx series, includes two devices. The first device, the BS85B12-3, has 12 touch keys together with a 48 LED and 56 pixel LCD display drive capability. The second device, the BS85C20-3, has 20 touch keys together with a 112 LED and 88 pixel LCD display drive capability. All touch key functions are implemented using fully internal oscillator circuits and timers. When human contact is detected, the change in oscillator external capacitance results in a change of oscillator frequency leading to a resulting timer value change. This feature coupled with a channel encoder for multiple-channel scanning, enables the touch switch functions within the BS85xxx series to detect which switches have been touched. One unique and special feature of the BS85xxx series devices is that external reference capacitors are not required as switch sensitivity is adjusted using the application program.

The BS85B12-3 and BS85C20-3 provide three system frequency selections of 8MHz, 12MHz and 16MHz and a dual SPI/I2C communication interface allowing the devices to act as both master and slave terminals. The devices can also directly drive 1/2 or 1/3 bias LCD display panels as well as LED displays which have current drive capabilities of 40mA sink current and -20mA source current. Additionally, the BS85B12-3 provides 2Kx15 of Flash Program Memory, 256 bytes of RAM Data Memory and up to 22 I/O lines that can directly drive a 48 (8x6) LED panel or 56 (14x4) pixel LCD display panel. The BS85C20-3 provides 4Kx15 of Flash Program Memory, 384 bytes of RAM Data Memory, up to 38 I/O lines that can directly drive a 112 (14x8) LED panel or 88 (22x4) pixel LCD display panels.


These new devices will be suitable for products requiring both keyboard inputs and LED or LCD display panel drivers, such as blenders, extractors, electric pressure cookers, disinfecting machines, intelligent refrigerators etc. The many internal special features of the devices offer the benefits of reduced PCB areas and simplified external circuitry.


The internal Watchdog Timer and Low Voltage Reset functions provide excellent immunity against malfunction or erroneous operation. Regarding device packaging, the BS85B12-3 is available in 24-pin SKDIP, 24-pin SOP, 24-pin SSOP, 28-pin SKDIP, 28-pin SOP and 28-pin SSOP packages while the BS85C20-3 is supplied in 28-pin SKDIP, 28-pin SOP, 28-pin SSOP and 44-pin QFP packages.