7

LASER Drive Mode

The laser is driven in pulsed mode during normal

operation. A calibration mode is provided which drives

the laser in continuous (CW) operation.

Eye Safety

The ADNS-7550 integrated molded lead-frame DIP

sensor and the associated components in the schematic

of Figure 5 are intended to comply with Class 1 Eye

Safety Requirements of IEC 60825-1.

PixArt Imaging

suggests that manufacturers perform testing to verify

eye safety on each mouse. It is also recommended to

review possible single fault mechanisms beyond those

described below in the section “Single Fault Detection”.

Under normal conditions, the sensor generates the drive

current for the VCSEL.

In order to stay below the Class 1 power requirements,

LASER_CTRL0 (register 0x1a), LASER_CTRL1 (register

0x1f ), LSRPWR_CFG0 (register 0x1c) and LSRPWR_CFG1

(register 0x1d) must be programmed to appropriate

values. The ADNS-7550 integrated molded lead-frame

DIP sensor which comprised of the sensor and VCSEL;

is designed to maintain the output beam power within

Class 1 requirements over components manufacturing

tolerances and the recommended temperature range

when adjusted per the procedure below and implement-

ed as shown in the recommended application circuit of

Figure 6. For more information, please refer to Eye Safety

Application Note AN 5361.

LASER Power Adjustment Procedure

1.

The ambient temperature should be 25C +/- 5C.

2.

3.

Set the Range bits (bit 7 and 6 of register 0x1f ) to

b’01.

4.

Set the Range_C1 and Range_C0 complement bits

(bit 7 and 6 of register 0x1f ) to b’10.

5.

Enable the Calibration mode by writing to bits [3,

2, 1] of register 0x1A so the laser will be driven with

100% duty cycle.

6.

Set the laser current to the minimum value

by

writing

0x00

to

register

0x1c,

and

the

complementary value 0xFF to register 0x1d.

7.

Program registers 0x1c and 0x1d with increasing

values to achieve an output power of not more than

506uW to meet class 1 Eye Safety over temperature.

If this power is obtained, the calibration is complete,

skip to step 11.

8.

If it was not possible to achieve the power target, set

the laser current to the minimum value by writing

0x00 to register 0x1c, and the complementary value

0xff to register 0x1d.

9.

Set the Range and Range_C bits in registers 0x1a

and 0x1f, respectively, to choose to the higher laser

current range.

10.

Program registers 0x1c and 0x1d with increasing

values to achieve an output power of not more than

506uW to meet class 1 Eye Safety over temperature.

11.

Save the value of registers 0x1a, 0x1c, 0x1d, and

0x1f in non-volatile memory in the mouse. These

registers must be restored to these values every

time the ADNS-7550 is reset.

12.

Reset the mouse, reload the register values from

non-volatile memory, enable Calibration mode,

and measure the laser power to verify that the

calibration is correct.

Good engineering practices such as regular power meter

calibration, random quality assurance retest of calibrated

mice, etc. should be used to guarantee performance, reli-

ability and safety for the product design.

LASER Output Power

The laser beam output power as measured at the naviga-

tion surface plane is specified below. The following con-

ditions apply:

1.

The system is adjusted according to the above

procedure.

2.

The system is operated within the recommended

operating temperature range.

3.

No allowance for optical power meter accuracy is

assumed.

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PixArt Imaging Inc.

PixArt Imaging Inc.

ADNS-7550 Integrated Molded Lead-Frame DIP Sensor