LDC - AD7147 Eval-Board

Q When we connected an AD7143-1 externally to AD7147-1 evaluation board (instead of AD7147-1), we noticed an automatic change in configuration/ID register of EEPROM. When we reconnected AD7147-1 (instead of AD7143-1) the configuration/ID register was not automatically changed back into "normal" value. A If you power down the eval board, and remove the external AD7143-1 board, the AD7147 board should power up correctly.

AD7147: Multiple devices in one application

Q How to handle multiple AD7147-1 (3) in one application? A We do not recommend to use multiple AD7147 in one application since we have observed in previous applications serious crosstalk issues when using multiple devices on the same sensor. The excitation source of one will couple onto the other device sensors and cause large noise problems;

Q 1) Using the AD7142 is it possible to put the buttons on another board connected by a cable? Or is it better to have a short distance between the buttons and the AD717x? 2) Do you have PCB layouts for buttons for the AD7147 with one electrode? The examples for the AD7142 uses mostly two electrode . 3) What is the major difference between the AD7142 and AD7147? A 1) Using the AD7142 is it possible to put the buttons on another board connected by a cable? Or is it better to have a short distance between the buttons and the AD717x? It is not possible to put the buttons on another board connected by cable using the AD7142, however this is possible with the AD7147. One of the new features of the AD7147 is the active shield that allows the sensors to be located remotely from the IC and provides shielding from another noise sources in the application. The maximum distance between the AD7147 and the sensor is 50 cm. 2) Do you have PCB layouts for buttons for the AD7147 with one electrode? The examples for the AD7142 uses mostly two electrode . The AD7147 is going to be released next month. The datasheet is already available online: http://www.analog.com/AD7147 I have attached the AD7147 sensor library in PADS format. 3) What is the major difference between the AD7142 and AD7147? The only different between AD7142 and AD7147 is the analog front end. The AD7142 has two electrodes and the AD7147 just one. The attached slides shows how the electric field is created in each case. Some of the AD7147 advantages are: Larger response, easier design and can tolerate thicker overlays.

AD7147: Can I use it to detect the hand at 10cm away from the button?

Q Is it possible to use the AD7147 for an approximation, I want to detect the hand at 10cm away from the button? A The proximity detection range for AD7147 is up to 2cm. Getting a detection distance of 10cm is not possible with the cap touch parts AD7147/8. We have other parts which offer more proximity distance range, AD7150/1 have 1 or 2 channels which can be dedicated to implement proximity detection with a range of up to 5cm. The range of the AD7150 is dependent on the actual sensor design/size/shape so it may be possible to extend the range with large sensor.

AD7147: Can several AD7147 be used in parallel to realize a remote control with 35 buttons?

Q Can several AD7147 be used in parallel to realize a remote control with 35 buttons? A Several AD7147 devices cannot be connected to the same sensor module or keypad design due to crosstalk and interference from the excitation signals of one device to another. The parts cannot be synchronised together to eliminate this crosstalk.

We have 8 AD7147 on operating on a single 2-layer PCB which......

Q We have 8 AD7147 on operating on a single 2-layer PCB which. Devices operate properly as long as only one AD7147 is exciting the electrodes. From the posts available at the ENGINEER zone I suspect the problem lies in the interference caused by the unsynchronized excitation signals. As our board space is quite limited, we can only have about 4 mm wide GND stripes between the AC shields. Would a 4-layer PCB with a bottom ground covering all the shields (moving the 2 layers currently used for routing and shielding the electrode signals to the two topmost PCB layers) sufficiently isolate the AD7147s. Alternatively, is there perhaps a way to synchronize the excitation signals? A I suspect that the excitation signals from each AD7147 are interfering with each other. Because they are not synchronized, if the sensors are close to each other, then the excitations will interfere, and cause noise in the sensor measurements. There are two options - if this is possible, you can modify your sensor design to keep the sensors controlled by each AD7147 apart, to reduce the interference. However, I guess this will not be possible if you are tight for space.

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AD7147A Obsolete
The AD7147A CapTouchâ„¢ controller is designed for use with capacitance sensors implementing functions such as buttons, scroll bars, and wheels. The sensors...
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AD7147A on Analog.com