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AD7148 Dataheets PDF



Part Number AD7148
Manufacturers Analog Devices
Logo Analog Devices
Description Programmable Touch Controller
Datasheet AD7148 DatasheetAD7148 Datasheet (PDF)

Programmable Touch Controller for Single Electrode Capacitance Sensors AD7148 FEATURES www.datasheet4u.com Programmable capacitance-to-digital converter (CDC) Femtofarad (fF) resolution 8 capacitance sensor inputs 25 ms update rate, all 8 sensor inputs No external RC components required Automatic conversion sequencer On-chip automatic calibration logic Automatic compensation for environmental changes Automatic adaptive threshold and sensitivity levels Register map compatible with AD7143 On-chip.

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Programmable Touch Controller for Single Electrode Capacitance Sensors AD7148 FEATURES www.datasheet4u.com Programmable capacitance-to-digital converter (CDC) Femtofarad (fF) resolution 8 capacitance sensor inputs 25 ms update rate, all 8 sensor inputs No external RC components required Automatic conversion sequencer On-chip automatic calibration logic Automatic compensation for environmental changes Automatic adaptive threshold and sensitivity levels Register map compatible with AD7143 On-chip RAM to store calibration data I2C-compatible serial interface Separate VDRIVE level for serial interface Interrupt output 16-lead, 4 mm × 4 mm LFCSP 2.6 V to 3.3 V supply voltage Low operating current Full power mode: 1 mA Low power mode: 21.5 μA FUNCTIONAL BLOCK DIAGRAM ACSHIELD VCC 5 8 GND 7 BIAS 6 AD7148 CIN0 13 CIN1 14 CIN2 15 CIN3 16 CIN4 CIN5 CIN6 CIN7 1 2 3 4 EXCITATION SOURCE CALIBRATION RAM 16-BIT Σ-Δ CDC POWER-ON RESET LOGIC SWITCH MATRIX CALIBRATION ENGINE CONTROL AND DATA REGISTERS SERIAL INTERFACE AND CONTROL LOGIC INTERRUPT AND GPIO LOGIC 9 10 11 12 VDRIVE SDA SCLK INT APPLICATIONS Cell phones Personal music and multimedia players Smart handheld devices Television, A/V, and remote controls Gaming consoles Digital still cameras Figure 1. GENERAL DESCRIPTION The AD7148 is designed for use with capacitance sensors implementing functions such as buttons, scroll bars, and wheels. The sensors need only one PCB layer, enabling ultrathin applications. The AD7148 is an integrated capacitance-to-digital converter (CDC) with on-chip environmental calibration. The CDC has eight inputs channeled through a switch matrix to a 16-bit, 250 kHz sigma-delta (∑-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 minimal 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 pickup in the sensor. For floating, or two, electrode sensors, use the AD7143. The AD7148 has on-chip calibration logic to compensate for changes in the ambient environment. The calibration sequence is performed automatically and at continuous intervals as long as the sensors are not touched. This ensures that there are no false or nonregistering touches on the external sensors due to a changing environment. The AD7148 has an I2C®-compatible serial interface, as well as an interrupt output. There is a VDRIVE pin to set the voltage level for the serial interface independent of 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 m.


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