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ELMOS Semiconductor AG

Data Sheet

QM-No.: 25DS0091E.00

PRELIMINARY INFORMATION - JUL 28, 2011

This document contains information on a pre-production product. ELMOS Semiconductor AG reserves the right to change specifications and information herein without notice.

INTEGRATED CIRCUIT FOR PIR SMART SENSOR

E910.97

Detailed Description__________________________________________

Fig 1: Block diagram of E910.97

PIR Sensor Input

A differential input stage provides for a direct

connection to a high impedance PIR sensor element.

The analog to digital converter generates a digital

signal from the voltage level measured between the

PIRIN and NPIRIN pins.

A band gap reference ensures a temperature and

supply voltage independent gain.

Voltage Regulator

The on-chip shunt regulator accepts a large range of

input currents. It generates a stable 3V supply for the

is taken from the integrated band gap reference.

Oscillator

The IC contains an on chip low power oscillator. The

frequency is set to 64kHz. The timing signals and

cutoff frequencies of the digital filters are derived from

this frequency.

Band-Pass Filter

A 2nd order low-pass filter with a cut-off frequency of

7Hz

eliminates

unwanted

higher

frequency

high pass filter with a 0.4Hz cut-off frequency.

Alarm Event Processor

The signal from the band pass filter is rectified. When

the signal level exceeds the set sensitivity threshold,

an internal pulse is generated. A second pulse is

counted, when the signals changes sign and exceeds

the threshold again.

Whenever 2 pulses appear within 2s, the REL output is

activated.

The voltage applied to the ONTIME input determines

how long the REL output stays active. The REL output

remains active from the first alarm condition to the last

alarm condition plus the time selected with the

ONTIME input.

LPF

Comparator

&

Alarm Event

Logic

BAND GAP

REF

PIR

ADC

Test Control Logic

NPIRIN

REL

VDD

GND

PIRIN

ON

TIME

SENS

HPF

OEN

OSC

PIN ADC

ENVREG