INTRODUCTION: how to improve water tolerance of A96T3A6
and how to use proximity sensor function
▶ How does the Shield CH operate to improve water tolerance?
- From GND perspective in Figure 1, water formed between an electrode and GND causes a dielectric between the two electrodes and leads the Cap value to become larger. Since this Cap features the same electrical characteristics as a finger touch, it can be recognized as a normal human touch.
[Figure 1.] Example Circuit Diagram when a Mesh Electrode Is Used as GND
- For Shield electrodes, water formed between an electrode and the Shield electrode causes a dielectric between the two electrodes and leads the Cap value to become larger. In this case, however, the electrode is connected not to GND but to Shield CH. If this Shield CH is driven with the same waveform as Touch CH, the voltage difference between the two electrodes is always ‘0’. This means that the Cap is formed but does not affect the Touch operation at all since there is no change of Charges.
[Figure 2.] Example Circuit Diagram when a Mesh Electrode Is Used as Shield
▶ Demonstration of A96T3A6 with Shield function before and after improving water tolerance
- Water Prevent performance is evaluated based on the use of Shield CH, using a TWS dedicated demo board with a T3A6 IC.
[Figure 3.] T3A6 Demo Board with Shield Function
1) In the same environment, CS01 uses the Shield function and CS03 does not use the Shield function.
2) When using the Shield function, the reactivity to water increases by approximately 10 times.
3) Compared to using GND, the use of the Shield CH improves the reactivity to finger touch by more than twice.
- Comparison of DiffData variations after spraying water:
[Figure 4.] DiffData Variation when Shield Is Disabled (GND) [Figure 5.] DiffData Variation when Shield Is Enabled (Touch)
▶ Proximity sensor application in HeadSet models
- The proximity sensor function is currently under development to be applied to HeadSet models.
- Channels are used as listed below:
1) Proximity 2-ch: Used for wearable sensing. To ensure the performance stability of wearable sensing, these two channels are designed in a top-to-bottom two channel structure.
2) Reference 1-ch: Used as an auxiliary channel for temperature/ humidity compensation.
3) Shield 1-ch: Designed to have a Shield structure to prevent malfunction caused by daily moisture, sweat, and etc.
[Figure 6.] Actual Use Case of Proximity Sensor Application