●Product Details
●The AD7877 is a 12-bit, successive approximation ADC with a synchronous serial interface and low on resistance switches for driving touch screens. The AD7877 operates from a single 2.7 V to 5.25 V power supply (functional operation to 2.2 V), and features throughput rates of 125 kSPS. The AD7877 features direct battery measurement on two inputs, temperature and touch-pressure measurement.
●The AD7877 also has an on-board reference of 2.5 V. When not in use, it can be shut down to conserve power. An external reference can also be applied and varied from 1 V to +VCC, with an analog input range of 0 V to VREF. The device includes a shutdown mode that reduces its current consumption to less than 1 μA.
●To reduce the effects of noise from LCDs, the acquisition phase of the on-board ADC is controlled via the STOPACQ pin. User-programmable conversion controls include variable acquisition time and first conversion delay. Up to 16 averages can be taken per conversion. There is also an on-board DAC for LCD back-light or contrast control. The AD7877 runs in either slave or master mode using a conversion sequencer and timer. It is ideal for battery-powered systems such as personal digital assistants with resistive touch screens and other portable equipment.
●The part is available in a 32-lead lead frame chip scale package (LFCSP), and a 25-ball wafer level chip scale package (WLCSP). AD7877W model is qualified for automotive applications.
●Applications
● Personal digital assistants
● Smart hand-held devices
● Touch screen monitors
● Point-of-sale terminals
● Medical devices
● Cell phones
● Pagers
●### Features and Benefits
● 4-wire touch screen interface
● LCD noise reduction feature (STOPACQ pin)
● Automatic conversion sequencer and timer
● User-programmable conversion parameters
● On-chip temperature sensor:
●−40°C to +85°C
● On-chip 2.5 V reference
● On-chip 8-bit DAC
● 3 auxiliary analog inputs
● 1 dedicated and 3 optional GPIOs
● 3 interrupt outputs
● 2 direct battery measurement channels (0.5 V to 5 V)
● Qualified for automotive applications
● See Data Sheet for additional features
