●Product Details
●The AD7879/AD7889 are 12-bit successive approximation analog-to-digital converters (SAR ADCs) with a synchronous serial interface and low on-resistance switches for driving 4-wire resistive touch screens. The AD7879/AD7889 work with a very low power supply—a single 1.6 V to 3.6 V supply—and feature a throughput rate 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 AD7879/AD7889 contain 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 AD7879/AD7889 can run in slave mode or standalone (master) mode, using an automatic conversion sequencer and timer.
●The AD7879/AD7889 have a programmable pin that can operate as an auxiliary input to the ADCs, as a battery monitor, or as a general-purpose input/output (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 AD7879/AD7889 offer temperature measurement and touch pressure measurement.
●The AD7879 is available in a 12-ball, 1.6 mm × 2 mm WLCSP and in a 16-lead, 4 mm × 4 mm LFCSP. The AD7889 is available in a backside coated version of the WLCSP. Both devices support an SPI interface (AD7879/AD7889) or an I2C interface (AD7879-1/ AD7889-1).
●Applications
● Personal digital assistants
● Smart handheld devices
● Touch screen monitors
● Point-of-sale terminals
● Medical devices
● Cell phones
●### Features and Benefits
● 4-wire touch screen interface
● 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
● 12-ball, 1.6 mm × 2 mm WLCSP
● 16-lead, 4 mm × 4 mm LFCSP
