Analog Devices AD7877 Product Info

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 +V_CC, with an analog input range of 0 V to V_REF. 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