PixArt Imaging Inc.
ADNS-7530 Integrated Molded Lead-Frame DIP Sensor
Disabling the LASER
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.
LASER_NEN is connected to the gate of a P-channel
MOSFET transistor which when ON connects V to the
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-
DD3
connect V
from the LASER.
DD3
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
If the XYLASER pin is shorted to V /RefA, this test will
DD3
fail and will be reported as a fault.
VDD3
Microcontroller
ADNS-7530
S
LASER
LASER_NEN
VCSEL+VE
G
DRIVER
VDD3
D
fault control
block
VCSEL
Serial port
voltage sensor
current set
VCSEL-VE
XYLASER
GND
Figure 8. Single Fault Detection and Eye-safety Feature Block Diagram
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
9
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