Z8FS021 datasheet(28/68 Pages) ZILOG

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PS028806-0315

White Light Detection

ZMOTION® Intrusion Detection

Product Specification

detection of White Light and stays set until cleared by the application. No other action is

required by the application.

Additionally, an Anti-Jam feature is available via bit 5 of the ePIR_ASC0 Register to pre-

vent intentional jamming of the detector. When Anti-Jam is on, the Engine looks for con-

tinuous white light events occurring within a short time span (for example, a malicious

intruder continuously flashing a bright light onto the detector). After 12 white light events

within a short time period, the Engine automatically begins ignoring the white light events

and returns to normal motion detection. The Engine begins responding to white light

events after a period without white light events.

When White Light Detection Mode is enabled by programming the White Light Threshold

bits in PIR Status/Control Register 2 (ePIR_SC2), the application is not required to per-

form any other functions. The PIR Engine performs all required tasks related to White

Light immunity. The White Light Detected bit in PIR Status/Control Register 1 simply

provides the application with an indication that a white light event has occurred.

LED Requirements

The PIR Engine uses the voltage generated by the LED connected to ANA1 to determine

the level of white light to which the system is being subjected. While most high-efficiency

LEDs will perform correctly for this function, there are certain requirements placed on the

specifications of the LED that is used in the system.

These requirements are:

• Do not place the LED behind any white light filtering material. If it is behind a lens or

a light pipe, these materials should be transparent to white light.

• Ensure that the light source for the LED is originating from the same general direction

as the PIR sensor. It is important that the PIR sensor and the LED receive the light at

the same time.

• LEDs are available with a large range of electrical specifications. The White Light

Threshold Detection bits in the ePIR_SC02 Register allow the PIR Engine the flexibil-

ity to work with many LED types, but generally LEDs that are more efficient at gener-

ating a voltage from a light source perform better as white light detectors.

• Most high-efficiency LEDs in red, yellow or green with a forward voltage drop less

than 2V @2mA are well suited for white light detection.

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