Is an air gap between sensor PCB and covering material allowed?

No air gap is allowed between the sensor PCB and the covering material or case of the product. Less of the electric field extends above the covering material when there is an air gap, and the field dissipates in air. These combine to decrease the sensor response. Also, the covering material may bend on contact, and the user may interfere with more or less of the electric field than before. This results in a non linear response from the sensor. These two effects combine to give an unpredictable response from sensor. We recommend 3M 467MP double-sided tape or similar to glue or tape the sensor PCB to covering plastic.

Can conductive material be placed directly on top of the sensors?

Conductive material interferes with the electric field generated by the AD7147, and so it is not recommended to place conductive material directly over the sensors.

2-layer or 4-layer PCB?

Choose a 4-layer PCB design when there is no room to route from the AD7147 to the sensors, outside of the sensor active areas. Nothing should be routed directly under the sensors or sensor traces. If there is room on the PCB to route to and from the AD7147 without interfering with the sensor traces, then a 2-layer PCB can be used.

Is an air gap between sensor PCB and covering material allowed?

No air gap is allowed between the sensor PCB and the covering material or case of the product. Less of the electric field extends above the covering material when there is an air gap, and the field dissipates in air. These combine to decrease the sensor response. Also, the covering material may bend on contact, and the user may interfere with more or less of the electric field than before. This results in a non linear response from the sensor. These two effects combine to give an unpredictable response from sensor. We recommend 3M 467MP double-sided tape or similar to glue or tape the sensor PCB to covering plastic.

How many sensors can I implement using one AD7147 device?

The number of sensors that can be implemented using one AD7147 depends on the type of sensors required. The AD7147 has 13 CIN inputs, and has 12 time based conversion stages. The table below gives a the number of input pins and the number of conversion stages required for each sensor type. Any number of sensors can be combined, as long as the total number of inputs required does not exceed 13, and the total number of conversions required does not exceed 12.

How far away from the sensor can proximity be detected?

Proximity can be detected up to a maximum of 20mm from the surface of the sensor, depending on the size of the sensor. The AD714x evaluation board can be used to experiment with proximity detection.

Is auto calibration possible?

Yes, the AD714x internal logic contains two calibration algorithms for correcting drift errors due to environmental (e.g., temperature and humidity) conditions.

What is the AD714x operating voltage range?

VCC = 2.6V to 3.6V
VDRIVE = 1.65V to 3.6V

What is the code space for a Slider?

Typically: 4990 bytes program memory, 254 bytes RAM

What is the code space for a Scroll Wheel?

Typically: 11k code memory , 667 bytes data memory

What is the IC temperature range?

The AD714x is specified at -40°C to +85°C.

What are Capacitive Sensors and how are they used?

Ask The Applications Engineer What are Capacitive Sensors and how are the used.

Download pdf

Should I be concerned about ESD?

The AD714x ESD Human Body Model is specified at 2.5kV.The AD714x sensors have been subjected to the ESD air discharge up to 15kV under both contact and non-contact conditions without any failures. Note: ESD events have to be carefully considered during development in order to prevent the ESD charge from coupling directly onto the AD714x sensor board circuits.

Can all sensors connected to the AD7147 be active at the same time?

The AD7147 takes a measurement on all sensors connected to it in a round robin fashion. All sensors can be measured within 36 ms. In practice, this allows the AD7147 to detect if sensors are active at the same time, as it is very unlikely the end user can activate/deactive a sensor within 36 ms.

Is there a power-up configuration?

Yes, the AD7147 BANK 2 connection set up registers and some BANK 1 set up registers have to be configured at start-up.

Is there a keep out area required around the sensor?

Yes. For grounded metal, the keep out is 0.2 mm. For floating metal, keep-out area is 5 cm. Floating metal closer to the sensors than 5 cm should be grounded.

Is there software required for buttons?

Yes. A few lines of code are required to ensure that, if an error occurs, for example on power-up, the part is recalibrated. Sample C code is available online.

Does Analog Devices provide the open source C-Code for sliders and scroll wheels?

Yes, the code is provided free of charge and royalties once the customer signs the AD714x SW licence agreement.

What is the maximum distance between sensor traces and AD7147?

Maximum distance between sensor trace and AD7147 CIN input pin is 50 cm. The AD7147 can be placed on a different PCB than the sensors, provided ACshield is used to shield around the sensor traces.

AD714x传感器能否在戴手套的情况下工作？

某些手套接触传感器时它能进行感测，但另一些不行。这取决于手套的厚度。 ADI公司测试了2 mm厚度的手套，结果传感器能工作。

什么时候应该使用交流屏蔽？

用来替代PCB板上传感器周围的接地层。当IC与传感器处于不同PCB时，要屏蔽传感器进出走线，应在全部传感器走线的周围、上方和下方使用交流屏蔽。

Which iCoupler product is best for my application?

Due to the unique nature of each application, the choice of which product to use is best left to the user. The selection tables available at www.analog.com/iCoupler should provide guidance for choosing the most appropriate iCoupler product. For additional assistance, please contact your local Analog Devices sales representative or distributor.

2层还是4层PCB？

在因空间不足而无法在传感器有效区域以外从AD7147到传感器布设走线时，应选择4层PCB设计。传感器和传感器走线正下方不得布设任何走线。如果PCB上的空间能容下AD7147进出走线而不干扰传感器走线，则可使用2层PCB板。

当手指大小不同的用户接触传感器时，会发生什么？

AD7147内置逻辑含有一种自适应阈值算法，能够自动适应用户手指大小，并相应调整阈值水平。

能实现自动校准吗？

能，AD714x内置逻辑含有两个校准算法，用于校正因环境条件（如温度、湿度）造成的漂移误差。

传感器周围需要设立禁区吗？

是的。对于接地金属，禁区为0.2 mm。对于浮动金属，禁区为5 cm。距离传感器不足5 cm的浮动金属应接地。

IC温度范围是多少？

AD714x的额定温度范围为-40°C至+85°C。

按钮需要软件吗？

是的。需要几行代码，以确保在发生错误时，比如在上电时，能够重新校准器件。示例C代码在网上有提供。

AD714x能否在潮湿环境下工作？

与任何电容传感器应用相似，该传感器的性能会受到水分或潮湿的影响。 AD7147内部环境算法可自动跟踪并校正湿度条件。 传感器上有水滴（包括水分达到饱和状态）将不会导致激活失败。 建议进行测试，以保证传感器性能满足目标应用的要求。

AD714x工作电压范围是多少？

VCC = 2.6V 至 3.6V
VDRIVE = 1.65V 至 3.6V

可以同时激活连接AD7147的传感器吗？

AD7147以轮询方式测量与其相连的传感器。 传感器均可在36 ms内测量。在实际使用中，这样可让AD7147检测传感器是否同时激活，因为最终用户不大可能在36 ms内激活/取消激活一个传感器。

AD714x有没有中断功能？

有。AD714x的中断可配置为在每次CDC转换周期结束时置位，也可配置为仅在用户接触传感器时置位。

ADI提供滑块和滚轮的开源C代码吗？

是的，只要客户签署AD714x软件许可协议，这些代码均免费提供，且不收取使用费。

近程检测的有效距离是到离传感器多远？

近程检测的有效距离是到离传感器表面20mm，具体取决于传感器的大小。可以用AD714x评估板来实验近程检测。

能把导电材料直接放在传感器上方吗？

导电材料会干扰AD7147产生的电场，因此，不建议把导电材料直接放在传感器上方。

是否需要进行上电配置吗？

是的，AD7147 BANK 2连接设置寄存器和部分BANK 1设置寄存器需要在启动时进行配置。

我需要注意ESD吗？

AD714x ESD人体模型的额定值为2.5kV。AD714x传感器在接触和非接触条件下，经受过最高15kV ESD空气放电测试，从未失败。注意：在开发过程中需要仔细考虑ESD事件，以防止ESD放电直接耦合到AD714x传感器板电路中。

使用一个AD7147器件时，可以部署多少个传感器？

可以用一个AD7147器件实现的传感器数量取决于所需传感器的类型。 AD7147具有13路CIN输入，并提供12个基于时间的转换级。 下表显示每种传感器所需的输入引脚数和转换级数。 任意数量的传感器都可以进行组合，只要所需的输入总数不超过13，且所需的转换级数的总数不超过12即可。

传感器PCB与覆盖材料之间可以有空隙吗？

传感器PCB与产品覆盖材料或外壳之间不要留有空隙。若存在空隙，延伸到覆盖材料上方的电场减少，并消散在空气中。这些因素会导致传感器响应速率下降。此外，覆盖材料也可能在接触时弯曲，用户对电场的干扰可能增多或减少。结果导致传感器出现非线性响应。这两种效应相结合，会导致传感器出现不可预测的响应。建议用3M 467MP双面胶带或类似物质将传感器PCB板粘到覆盖塑料上。

Will the AD714x sensors work with a glove?

Some gloves will work while contacting the sensors but some gloves will not, depending on the thickness of the glove. ADI have tested gloves of 2 mm thickness and have found this to work successfully.

滑块的代码需要多少空间？

一般为：4990字节的程序存储器，254字节的RAM

传感器走线与AD7147之间的距离最长为多少？

传感器走线与AD7147 CIN输入引脚之间的最远距离为50 cm。AD7147可放置在与传感器不同的PCB上，但前提是采用交流屏蔽为传感器走线周围提供屏蔽。

滚轮的代码需要多少空间？

一般为：11k的代码存储器，667字节的数据存储器

当把一根手指放在两个传感器按钮上时，会发生什么？

如果这两个按钮相邻，而且从未想过要同时激活，则可以差分方式配置AD7147 CDC转换器级，以消除用户同时接触两个按钮所造成的影响。另外，AD7147可以配置为同时激活这两个传感器触点。

When should I use AC shield?

Use instead of a ground plane around the sensors on the PCB. To shield traces to/from the sensors when the IC is not on the same PCB as the sensor, use around, above and below all sensor traces.

What happens when a finger is placed across two sensor buttons?

If the two buttons are adjacent to each other and never meant to be activated at the same time, the AD7147 CDC converter stages can be configured differentially to null out the effects of a user simultaneously touching two buttons. Alternatively, the AD7147 can be configured to register both sensor contacts at the same time.

What happens when users with different finger sizes contact the sensor?

The AD7147 internal logic contains an Adaptive Threshold algorithm that automatically adapts to the users finger size and readjusts the threshold levels accordingly.

Does the AD714x have an interrupt?

Yes, the AD714x interrupt can be configured to be asserted at the end of each CDC conversion cycle or only upon user contact with a sensor.

Can the AD714x work under wet/humid conditions?

Like any capacitive sensor application, the sensors performance will be affected by water and humidity. The AD7147 internal environmental algorithms will automatically track and correct for humidity conditions. Water on the sensors (including saturated) will not cause a false activation. We recommend testing to ensure the sensor performance is satisfactory for the required application