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.
|Title||Content Type||File Type|
|AD7877: Touch Screen Controller Data Sheet (Rev D, 12/2011) (pdf, 795 kB)||Data Sheets|
|AN-753: Configuring the AD7877 (pdf, 247 kB)||Application Notes|
|AN-766: Using the Noise Reduction Feature on the AD7877 (pdf, 409 kB)||Application Notes|
|AN-738: Using the AD7877 Touch Screen Controller and the Intel PXA250 Processor Under Windows CE.NET (pdf, 60 kB)||Application Notes|
|MS-2210: Designing Power Supplies for High Speed ADC (pdf, 327 kB)||Technical Articles|
As Systems Shrink in Size, Input Becomes More Difficult
... For direct input on a display, like in the case of a Palm-like PDA, Analog Devices offers its AD7877 touch-screen digitizer. (Portable Design, 6/2003)
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|LEADING Semiconductors for Wireless Handsets Brochure (pdf, 1923 kB)||Overview|
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|AD7877 Input Touch Screen Controller Linux Driver (Wiki Site)||Device Drivers||HTML|
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