 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
QT1+T+G Datasheet(PDF) 4 Page - Quantum Research Group |
|
||||||||||||||||||||||||||||||
QT1+T+G Datasheet(HTML) 4 Page - Quantum Research Group |
|
|
4 / 14 page  1.3.5.2 Changing Cs, Cx The values of Cs and Cx have a dramatic effect on sensitivity, and Cs can be easily increased in value to improve gain. Sensitivity is directly proportional to Cs and inversely proportional to Cx: S = k$CS CX Where ‘k’ depends on a variety of factors including the gain pin setting (see prior section), Vdd, etc. Sensitivity plots are shown in Figures 4-1 and 4-2, page 10. 1.3.5.3 Electrode / Panel Adjustments Sensitivity can often be increased by using a bigger electrode, or reducing overlying panel thickness. Increasing electrode size can have a diminishing effect on gain, as the attendant higher values of Cx will start to reduce sensor gain. Also, increasing the electrode's surface area will not substantially increase touch sensitivity if its diameter is already much larger in surface area than the object being detected. The panel or other intervening material can be made thinner, but again there are diminishing rewards for doing so. Panel material can also be changed to one having a higher dielectric constant, which will help propagate the field through to the front. Locally adding some conductive material to the panel (conductive materials essentially have an infinite dielectric constant) will also help; for example, adding carbon or metal fibers to a plastic panel will greatly increase frontal field strength, even if the fiber density is too low to make the plastic bulk-conductive. 1.3.5.3 Ground Planes Grounds around and under the electrode and its SNS trace will cause high Cx loading and destroy gain. The possible signal-to-noise ratio benefits of ground area are more than negated by the decreased gain from the circuit, and so ground areas around electrodes are discouraged. Keep ground, power, and other signals traces away from the electrodes and SNS wiring 2 - QT118H SPECIFICS 2.1 SIGNAL PROCESSING The QT118H digitally processes all signals using a number of algorithms pioneered by Quantum. The algorithms are specifically designed to provide for high survivability in the face of all kinds of adverse environmental changes. 2.1.1 DRIFT COMPENSATION ALGORITHM Signal drift can occur because of changes in Cx and Cs over time. It is crucial that drift be compensated for, otherwise false detections, non-detections, and sensitivity shifts will follow. Drift compensation (Figure 2-1) is performed by making the reference level track the raw signal at a slow rate, but only while there is no detection in effect. The rate of adjustment must be performed slowly, otherwise legitimate detections could be ignored. The QT118H drift compensates using a slew-rate limited change to the reference level; the threshold and hysteresis values are slaved to this reference. Once an object is sensed, the drift compensation mechanism ceases since the signal is legitimately high, and therefore should not cause the reference level to change. The QT118H's drift compensation is 'asymmetric': the reference level drift-compensates in one direction faster than it does in the other. Specifically, it compensates faster for decreasing signals than for increasing signals. Increasing signals should not be compensated for quickly, since an approaching finger could be compensated for partially or entirely before even touching the sense pad. However, an obstruction over the sense pad, for which the sensor has already made full allowance for, could suddenly be removed leaving the sensor with an artificially elevated reference level and thus become insensitive to touch. In this latter case, the sensor will compensate for the object's removal very quickly, usually in only a few seconds. 2.1.2 THRESHOLD AND HYSTERESIS The internal signal threshold level can be set to one of three settings (Table 1-1). These are fixed with respect to the internal reference level, which in turn moves in accordance with the drift compensation mechanism. The QT118H employs a hysteresis dropout below the threshold level of 17% of the delta between the reference and threshold levels. 2.1.3 MAX ON-DURATION If an object or material obstructs the sense pad the signal may rise enough to create a detection, preventing further operation. To prevent this, the sensor includes a timer which monitors detections. If a detection exceeds the timer setting, the timer causes the sensor to perform a full recalibration. This is known as the Max On-Duration feature. After the Max On-Duration interval, the sensor will once again function normally, even if partially or fully obstructed, to the best of its ability given electrode conditions. There are two timeout durations available via strap option: 10 and 60 seconds. 2.1.4 DETECTION INTEGRATOR It is desirable to suppress detections generated by electrical noise or from quick brushes with an object. To accomplish this, the QT118H incorporates a detect integration counter lq 4 QT118H R1.08 / 0405 Pin 7 Low Pin 6 Medium Leave open High Tie Pin 5 to: Gain Table 1-1 Gain Strap Options Figure 2-1 Drift Compensation T hre sh old Signal Hysteres is Refer ence Ou tpu t |
Similar Part No. - QT1+T+G |
|
Similar Description - QT1+T+G |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
allmanual.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
