The AD7148 CapTouch™ Programmable Controller is designed for use with capacitance sensors implementing functions such as buttons, scroll bars, and wheels. The sensors need only one PCB layer, enabling ultra thin applications.
The AD7148 is an integrated capacitance-to-digital converter (CDC) with on-chip environmental calibration. The CDC has 8 inputs channeled through a switch matrix to a 16-bit, 250 kHz sigma-delta (Σ-Δ) converter. The CDC is capable of sensing changes in the capacitance of the external sensors and uses this information to register a sensor activation. The external sensors can be arranged as a series of buttons, as a scroll bar or wheel, or as a combination of sensor types. By programming the registers, the user has full control over the CDC setup.
High resolution sensors require minor software to run on the host processor.
The AD7148 is designed for single electrode capacitance sensors (grounded sensors.) There is an active shield output to minimize noise pick-up in the sensor. For floating, or two electrode sensors, use the AD7143.
The AD7148 has on-chip calibration logic to account for changes in the ambient environment. The calibration sequence is performed automatically and at continuous intervals, while the sensors are not active. This ensures that there are no false or non-registering touches on the external sensors due to a changing environment.
The AD7148 has an I2C-compatible serial interface, as well as interrupt output. There is a VDRIVE pin to set the voltage level for the serial interface independently from VCC.
The AD7148 is available in a 16-lead, 4 mm × 4 mm LFCSP and operates from a 2.6 V to 3.6 V supply. The operating current consumption in low power mode is typically 26 μA.
|Title||Content Type||File Type|
|AD7148: Programmable Touch Controller for Single Electrode Capacitance Sensors Data Sheet (Rev A, 01/2010) (pdf, 1236 kB)||Data Sheets|
|AN-925: Sensors for the AD7147 and AD7148 CapTouch® Controllers (pdf, 189 kB)||Application Notes|
|AN-957: Layout Guidelines for the AD7147 and AD7148 CapTouch® Controllers (pdf, 337 kB)||Application Notes|
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CapTouch Software License Agreement
(pdf, 15 kB)
Dowloading and opening the software implies acceptance of the Analog Devices software license agreement
Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.
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