Analog Devices

The AD7879 /AD7889are 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).APPLICATIONSPersonal digital assistantsSmart handheld devicesTouch screen monitorsPoint-of-sale terminalsMedical devicesCell phones

The AD7887 is a high speed, low power, 12-bit analog-to-digital converter (ADC) that operates from a single 2.7 V to 5.25 V power supply. The AD7887 is capable of 125 kSPS throughput rate. The input track-and-hold acquires a signal in 500 ns and features a single-ended sampling scheme. The output coding for the AD7887 is straight binary, and the part is capable of converting full power signals of up to 2.5 MHz.The AD7887 can be configured for either dual- or single-channel operation via the on-chip control register. There is a default single-channel mode that allows the AD7887 to be operated as a read-only ADC. In single-channel operation, there is one analog input (AIN0) and the AIN1/VREFpin assumes its VREFfunction. This VREFpin allows the user access to the part’s internal 2.5 V reference, or the VREFpin can be overdriven by an external reference to provide the reference voltage for the part. This external reference voltage has a range of 2.5 V to VDD. The analog input range on AIN0 is 0 to VREF.In dual-channel operation, the AIN1/VREFpin assumes its AIN1 function, providing a second analog input channel. In this case, the reference voltage for the part is provided via the VDDpin. As a result, the input voltage range on both the AIN0 and AIN1 inputs is 0 to VDD.CMOS construction ensures low power dissipation of typically 2 mW for normal operation and 3 μW in power-down mode. The part is available in an 8-lead, 0.15-inch-wide narrow body SOIC and an 8-lead MSOP package.Product HighlightsSmallest 12-bit dual-/single-channel ADC; 8-lead MSOP package.Lowest power 12-bit dual-/single-channel ADC.Flexible power management options, including automatic power-down after conversion.Read-only ADC capability.Analog input range from 0 V to VREF.Versatile serial input/output port (SPI/QSPI/MICROWIRE/ DSP compatible).ApplicationsBattery-powered systems (personal digital assistants, medical instruments, mobile communications)Instrumentation and control systemsHigh speed modems

TheAD7879/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).ApplicationsPersonal digital assistantsSmart handheld devicesTouch screen monitorsPoint-of-sale terminalsMedical devicesCell phones