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IQS243 Datasheet(PDF) 4 Page - List of Unclassifed Manufacturers |
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4 / 30 page ProxSense ® Series Copyright © Azoteq 2014 IQS243 Datasheet v1.5 Page 4 of 30 All Rights Reserved August 2014 Please refer to the Application Note Section on the Azoteq website for more design tips and other application dependent recommendations. 6 Adjustable Proximity Threshold The proximity threshold is selected by the designer to obtain the desired proximity sensitivity and is selectable between 1 (most sensitive) to 254 (least sensitive). The IQS243 has a default proximity threshold (PTH) of 4 for all channels. Proximity thresholds for the sense electrodes are individually adjustable between the specified limits. A proximity event is identified when for at least 6 consecutive samples the following equation holds: PTH =< LTA-CS Where LTA is the Long Term Average 7 Adjustable Touch Thresholds The touch threshold is selected by the designer to obtain the desired touch sensitivity and is selectable between 1/255 (most sensitive) to 254/255 (least sensitive). The IQS243 has a default touch threshold (TTH) of 32/255 (for all 3 channels). The touch threshold is expressed as a fraction of the LTA as follows: TTH = Selected Touch Threshold x LTA Where LTA is the Long Term Average The touch event is triggered based on TTH, CS and LTA. A touch event is identified when for at least 2 consecutive samples the following equation holds: TTH =< LTA-CS With lower average CS (therefore lower LTA) values the touch threshold will be lower and vice versa. Individual touch threshold can be set for each channel. 8 Charge Transfers The IQS243 samples in 4 timeslots. The charge sequence is shown in Figure 8.1, where CH0 is the Prox channel, which charges before each of the 3 input channels. CH0 is realised by connecting all three touch electrodes with internal switches. Therefore: CH0 is a distributed electrode formed by the 3 touch electrodes. Proximity can be detected by the distributed electrode (CRX0+CRX1+CRX2) AND each individual sense electrode (CRX0, CRX1 and CRX2). 9 I2C Communication The IQS243 device interfaces to a master controller via a 2 wire serial interface bus that is I 2CTM compatible. An optional RDY pin is available to indicate the communication window (required for Event Mode). The IQS243 has four available sub addresses, 44H (default) to 47H that is selected upon purchase of the IC. The ADR0 pin can also be pulled low to increase the I2C address by one decimal value (for example from 44H to 45H). The maximum I 2CTM compatible communication speed for the IQS243 is 400kbit/s. Please refer to the IQS243 Communications Interface and Sample Code Document for further details. |
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Similar Description - IQS243_15 |
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