AN607

10

Rev. 1.7

3.7. ESD Considerations

It is desirable to expose the Si70xx sensor to the environment. For the sensor to respond to the environment there

must be a way for the air being sensed to reach the sensor (the environmental access port). This means that the

sensor may also be exposed to ESD as specified in IEC 61000-4-2 with ESD peak voltage of up to ±15 kV.

For the humidity sensors, when the cover is not used and the ESD source is directly over the package opening, it is

possible for ESD to arc into the sensor area and cause damage. This can be avoided by using of the Silicon Labs

filter cover or by placing the Si70xx so that the sensor opening is offset from the environmental access port.

The above approaches will prevent ESD discharge into the sensor area, but ESD discharge to the leads may still

be possible. The best practice for ESD protection of the leads is to arrange the sensor placement and

environmental access so that high-level ESD events will preferentially be directed to ground (i.e., have an exposed

ground trace or ground shield closer to the environmental access port than the sensor). If grounded, a metal case

is used; this is also effective for ESD protection.

If it is not possible to protect the leads of the device from ESD, unused leads should be connected to VDD. High-

quality ESD protection diodes can be used on leads that have signals on them. The ESD protection device should

be rated for more than 15 kV immunity and should limit ESD voltage peaks to less than 10 V. Some examples that

have been tested include Vishay MSP3V3 and COMCHIP CPDQ3V3U-HF.