ADI AD7879WARUZ-RL

The AD7879W is a 12-bit successive approximation analog-todigital converters (SAR ADCs) with a synchronous serial interface and low on-resistance switches for driving 4-wire resistive touch screens. The AD7879W works with a very low power supply—a single 1.6 V to 3.6 V supply—and feature throughput rates of 105 kSPS. The devices include a shutdown mode that reduces current consumption to less than 6 μA. To reduce the effects of noise from LCDs and other sources, the AD7879W contains a preprocessing block. The preprocessing function consists of a median filter and an averaging filter. The combination of these two filters provides a more robust solution, discarding the spurious noise in the signal and keeping only the data of interest. The size of both filters is programmable. Other user-programmable conversion controls include variable acquisition time and first conversion delay; up to 16 averages can be taken per conversion. The AD7879W can run in slave mode or standalone (master) mode, using an automatic conversion sequencer and timer. The AD7879W has a programmable pin that can operate as an auxiliary input to the ADC, as a battery monitor, or as a GPIO. In addition, a programmable interrupt output can operate in three modes: as a general-purpose interrupt to signal when new data is available (DAV), as an interrupt to indicate when limits are exceeded (INT), or as a pen-down interrupt when the screen is touched (PENIRQ). The AD7879W offers temperature measurement and touch-pressure measurement. The AD7879W is available in a 16-lead, 4.4 mm×5.0 mm TSSOP and 16-lead 4 mm×4 mm LFCSP. Both packages support an SPI interface (AD7879W) or an I²C interface (AD7879-1W).

• 4-wire touch screen interface
• Qualified for automotive applications
• 1.6 V to 3.6 V operation
• Median and averaging filter to reduce noise
• Automatic conversion sequencer and timer
• User-programmable conversion parameters
• Auxiliary analog input/battery monitor (0.5 V to 5 V)
• 1 optional GPIO
• Interrupt outputs (INT, PENIRQ)
• Touch-pressure measurement
• Wake-up on touch function
• Shutdown mode: 6 μA maximum
• 16-lead, 4.4 mm×5 mm TSSOP
• 16-lead, 4 mm×4 mm LFCSP

• Automotive applications
• Personal digital assistants
• Smart handheld devices
• Touch screen monitors
• Point-of-sale terminals
• Medical devices
• Cell phones