Maxim Integrated Products introduces the MAX11810 and MAX11811, touch-interface systems with integrated 4-wire touch-screen controllers, haptic controller drivers, and infrared-based proximity sensing. These devices can drive a DC motor directly or piezo elements using an external piezo driver. The MAX11800 and MAX11801 are register-map-compatible versions without haptic controller drivers and proximity sensing. Through register programming, the MAX11810/MAX11811 generates greater than 50,000 different haptic patterns with a built-in haptic waveform generator.
Programmable registers eliminate the need for a dedicated interface on the application processor or system microcontroller. This programmability simplifies the addition of haptic feedback to any end equipment with a touch screen. Ideal applications include cell phones, MP3 players, portable media players, digital photo frames, multifunction printers, point-of-sale and financial terminals, bar code-scanners, card readers, and other industrial equipment. Automotive-qualified part versions exist for use in car GPS, entertainment head units, and rear-seat entertainment systems.
Traditional Haptic Feedback System
The current market solution for haptic feedback using motors requires the application processor/system microcontroller to drive the motor. The applications processor/microcontroller needs to generate the haptic waveforms and send them to the motor through a dedicated interface. This adds latency and engages the application processor/microcontroller continuously, not allowing it to perform other duties.
Simplified Haptic Feedback System
The MAX11810/MAX11811 has a built-in waveform generator that creates the various haptic patterns and provides a direct interface to the motors. This approach eliminates the need for a dedicated interface on the application processor/microcontroller. With an integrated H-bridge driver, the MAX11810/MAX11811 eliminates the need for an external amplifier when haptic feedback is implemented using a DC motor. Alternatively, if piezo elements are used to implement haptics, the MAX11810/MAX11811's haptic-feedback output drives an external high-voltage amplification circuit to which the piezo actuators are connected.
Automatic Validation of Touch Responses
Unlike existing touch-screen controllers, the MAX11810/MAX11811 and MAX11800/MAX11801 reduce system power by offering additional, digital, on-chip processing to validate touch events before they are sent to the application processor. This automatic validation reduces interrupt servicing of false or redundant touch events and lowers total system power. This capability is crucial for battery-powered end equipment. The MAX11800/MAX11801 and MAX11810/MAX11811 support a built in dynamic aperture feature (position hysteresis) and on-chip FIFO. This automatic function reduces latency in the touch response and unnecessary data transfer between the devices and application processor or microcontroller.
Two other touch-screen controllers are part of this device family, the MAX11802/MAX11803. These devices are register-map-compatible versions of the MAX11800/01 but without the position hysteresis and on-chip FIFO. MAX11802/11803 provides standard resistive, touch-screen controller functionality. Available in high-speed (25MHz) SPI and fast (400kHz) I²C versions, all these devices guarantee compatibility with virtually any system or application processor. A wide, 1.7V to 3.6V, single-supply operating range eliminates the need for external supply-voltage regulators and level translators on the data bus. The parts are offered in extended temperature range (-40°C to +85°C). A variant up to +105°C is currently being qualified for use in automotive applications.
The MAX11800–MAX11803 are available in 1.6mm x 2.1mm, 12-pin TQFN and 12-pin WLP packages. The MAX11810/MAX11811 are available in 2.1mm x 2.1mm, 20-pin TQFN and 16-pin WLP packages. These small package footprints facilitate the miniaturization of end equipment. To speed design-in, EV (evaluation) kits are available. To enable full system emulation, the EV kits come with a resistive touch panel. The EV kits for the MAX11810/MAX11811 add a DC motor for evaluating the tactile feedback capability of these devices.
The recommended price for the MAX11810 is $1.81 (1000-up, FOB, USA) and $1.76 (1000-up, FOB, USA) for the MAX11811. The recommended prices for the other devices in this controller family are: MAX11800, $1.51 (1000-up, FOB, USA); MAX11801, $1.46 (1000-up, FOB, USA); MAX11802, $1.31 (1000-up, FOB, USA); and MAX11803, $1.26 (1000-up, FOB, USA).
