qt220 Quantum Research Group, qt220 Datasheet
qt220
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qt220 Summary of contents
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... PC Peripherals ! Backlighted buttons The QT220 charge-transfer (“QT’”) QTouch self-contained digital sensor IC capable of detecting near-proximity or touch on two electrodes. It allows electrodes to project independent sense fields through any dielectric like glass, plastic, stone, ceramic, and wood. It can also turn metal-bearing objects into intrinsic sensors, making them responsive to proximity or touch. ...
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... QT220 Specifics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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... Overview 1.1 Introduction QT220 devices are burst mode digital charge-transfer (QT) sensor ICs designed specifically for touch controls; they include all hardware and signal processing functions necessary to provide stable sensing under a wide variety of conditions. Only a single low cost capacitor per channel is required for operation. ...
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... Rs resistors have no effect on sensitivity and should not be altered. Load capacitances can also be added to overly sensitive channels to ground, to reduce their gains. These should be in the order of a few picofarads. 2 QT220 Specifics 2.1 Signal Processing 2.1.1 Introduction These devices process all signals using 16 -bit math, using a number of algorithms pioneered by Quantum ...
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... Cx should be below 50pF to prevent errors; this value can be read with a conventional capacitance meter with the QT220 removed. The option setting resistors are mandatory and cannot be deleted. They must be strapped to either Vdd or Vss. ...
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... A sync pulse on SYNC/SS in slow mode acts to break the QT220 out of its sleep state between bursts, and to do another burst. The device will then go back to sleep again and await a new SYNC pulse Sync pulse does not arrive within about 90ms, it will wake again and run normally ...
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... If the supply voltage drifts or shift quickly, the drift compensation mechanism will not be able to keep up, causing sensitivity anomalies or false detections. The QT220 will track slow changes in Vdd, but can be seriously affected by rapid voltage steps. If the supply is shared with another electronic system, care should be taken to assure that the supply is free of digital spikes, sags, and surges which can cause adverse effects ...
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... Higher values of Rsns will make crosstalk problems worse; try to keep Rsns to 22K or less if possible. In general try to keep the QT220 close to the electrodes and reduce the adjacency of the sense wiring to ground planes and other signal traces; this will reduce the Cx load, reduce interference effects, and increase signal gain ...
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... Fosc; fast mode only; Circuit of Figure 1.2 bursts Fast mode only Notes Units mA Fast mode µA Slow mode, no Sync V/s Req’d for startup, w/o reset circuit V /RES V /RES V SYNC V SYNC V OUTn, 4mA sink V OUTn, 1mA source µA OPT1, OPT2, OPT3 bits QT220R R1.03/1006 O C ...
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... Nominal timing dependent on Fosc, Sync ms/level Nominal timing dependent on Fosc, Sync secs Nominal timing dependent on Fosc, Sync Option pin selected; secs Nominal timings; dependent on Fosc, Sync B A ø G Base level Metric (mm) Min Typ 7.39 4.98 0.23 6.88 1. 0.650 0.10 0.66 0.10 8º 0º QT220R R1.03/1006 H Max 8.20 5.59 0.38 7.49 1.85 - 0.25 0.86 0.20 8º ...
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... Marking QT220-ISSG xxxx = fab code 4.8 Moisture Sensitivity Level (MSL) MSL Rating MSL3 LQ Part Temperature Range -40 - 85C QT220-IG © QRG xxxxR 1 Peak Body Temperature O 260 C 11 Package SSOP-20 Specifications IPC/JEDEC J-STD-020C QT220R R1.03/1006 ...
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This device is covered under one or more United States and corresponding international patents. QRG patent numbers can be found online at www.qprox.com. Numerous further patents are pending, which may apply to this device or the applications thereof. The ...