9

Disabling the LASER

LASER_NEN is connected to the gate of a P-channel

LASER. In normal operation, LASER_NEN is low. In the

case of a fault condition (ground or VDD3 at XYLASER),

LASER_NEN goes high to turn the transistor off and dis-

Single Fault Detection

ADNS-7530 is able to detect a short circuit or fault

condition at the XYLASER pin, which could lead to

excessive laser power output. A path to ground on this

Figure 8. Single Fault Detection and Eye-safety Feature Block Diagram

pin will trigger the fault detection circuit, which will turn

off the laser drive current source and set the LASER_NEN

output high. When used in combination with external

components as shown in the block diagram below, the

system will prevent excess laser power for a resistive

path to ground at XYLASER by shutting off the laser. In

addition to the ground path fault detection described

above, the fault detection circuit is continuously

checking for proper operation by internally generating a

path to ground with the laser turned off via LASER_NEN.

fail and will be reported as a fault.

LASER_NEN

GND

ADNS-7530

LASER

DRIVER

VDD3

VCSEL

Microcontroller

Serial port

voltage sensor

current set

VDD3

fault control

block

VCSEL+VE

D

S

G

VCSEL-VE

XYLASER

PixArt Imaging Inc.

ADNS-7530 Integrated Molded Lead-Frame DIP Sensor

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PixArt Imaging Inc.