AT42QT1085 haptic architecture
Recommended ERM placement
Recommended drive electronics
Atmel has been big into touch sensing from the start including multitouch support (see Multitouch Chip For Mobile Handles Up To 16 Touches). The new AT42QT1085 follows in the footsteps of standalone touch sensor chips that provide capacitive button and scroll support. This approach offloads the host processor and provides a consistent device interface. The AT42QT1085 supports 8 channels but adds haptic feedback to the mix (Fig. 1). The touch sensing utilizes Atmel's QTouch charge transfer technology.
Atmel has partnered with Immersion to deliver 14 different haptic affects using the AT42QT1085. These range from stong to medium buzz to double click feedback. Each channel can handle a button or multiple channels can provide slider control. The chip has a dedicated PWM and pins to control power amplifier and haptic excentric rotating mass (ERM) motor.
Atmel does not just provide a chip. It also provides recommendations such as the placement of the ERM motor (Fig. 2). The ERM selection is based on the end product's mass, size, operating voltage and mounting location.
Atmel recommends two bipolar ampliers for the drive motor. These can be overdriven and in either direction. Recommended drive electronics include Texas Instruments TPA6205 and DRV8601 (Fig. 3).