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 (0.5V to 5V)
- Qualified for automotive applications
- See Data Sheet for additional features
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.
- Personal digital assistants
- Smart hand-held devices
- Touch screen monitors
- Point-of-sale terminals
- Medical devices
- Cell phones
Markets and Technologies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Software & Systems Requirements
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
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