MLX90711

Position/movement Sensing Auto-Shutoff

MLX90711 Position/movement Sensing Auto-Shutoff Page 8

Rev 1.0

15/Sep/00

Application Example

PCB

VSS

VDD1

RD

LEDP

SUM

CA1

CA0

90711

L

Load

N

R1

D1

LED1

D2

C1

REL1

The above drawing shows the electrical schematic of a typical application.

The asic is directly connected to the AC line via a resistor R1 and diode D1, thus supplying the asic during

only the positive cycle of the AC line voltage. A capacitor C1 is therefore added between VDD1 and VSS to

smooth the asic supply voltage. The asic will limit the voltage at VDD1 at approximately 60V. A 12V relay

REL1 can be used to load the pin RD. The relay is driven with a well defined duty cycle to ensure that the re-

lay is driven with the right energy. The relay driver needs a flyback diode D2. A led LED1 can be added to

indicate the state of the asic. If no led is used, it must be replaced by a short circuit.

Special care must be paid to the layout of the sensor on the pcb and to the connections between sensor and

asic. The asic is designed to detect very small variations in capacitance in the sensor. Therefore parasitic ca-

pacitances must be kept as small as possible, and injection of noise must be avoided.