FDC2114RGHT datasheet(46/60 Pages) TI1

46 / 60 page

FDC2212, FDC2214, FDC2112, FDC2114

SNOSCZ5A – JUNE 2015 – REVISED JUNE 2015

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Greater current savings can be realized by use of shutdown mode during inactive periods. In shutdown mode,

device configuration is not retained, and so the device must be configured for each sample. For this example,

configuring each sample takes approximately 1.2 ms (13 registers * 92.5 µs per register). The total active time is

20.6 ms. The average current is 20 ms * 3.6 mA active current + 980 ms * 2 µA of shutdown current, which is

approximately 75 µA of average supply current.

10.3 Do's and Don'ts

•

Do leave a small gap between sensor plates in differential configurations. 2-3mm minimum separation is

recommended.

•

The FDC does not support hot-swapping of the sensors. Do not hot-swap sensors, for example by using

external multiplexers.

11 Power Supply Recommendations

The FDC requires a voltage supply within 2.7 V and 3.6 V. Multilayer ceramic bypass X7R capacitors of 0.1

μF

and 1

μF between the VDD and GND pins are recommended. If the supply is located more than a few inches

from the FDC, additional bulk capacitance may be required in addition to the ceramic bypass capacitors. An

electrolytic capacitor with a value of 10

μF is a typical choice.

The optimum placement is closest to the VDD and GND pins of the device. Care should be taken to minimize the

loop area formed by the bypass capacitor connection, the VDD pin, and the GND pin of the device. See

Figure 63 and Figure 63 for a layout example.

12 Layout

12.1 Layout Guidelines

•

Avoid long traces to connect the sensor to the FDC. Short traces reduce parasitic capacitances between

sensor inductor and offer higher system performance.

•

Systems that require matched channel response need to have matched trace length on all active channels.

12.2 Layout Example

Figure 63 to Figure 66 show the FDC2114 / FDC2214 evaluation module (EVM) layout.

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Product Folder Links: FDC2212 FDC2214 FDC2112 FDC2114

FDC2114RGHT Datasheet(PDF) 46 Page - Texas Instruments