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5

Analog Technologies

ATLS500MA106

Low Noise Constant Current Laser Controller

Power Supply 5V

Power Supply 0V

To ADC

To ADC

1

2

D1

Laser Diode

1

2

D2

LED

Loop Good Indication

SBDN

1

GND

2

2.5VR

3

LIMS

4

LIS

5

LIO

6

VPS 12

PGND 11

LDC

10

LDA 9

TMPO 8

LPGD 7

ATLS500MATF

3

W1

20K

3

W2

20K

C1

1uFto 10uF

Current Set (Clock-wise)

Current Limit Set (Clock-Wise)

1

2

R1 100K

1

2

3

S1

SPDT

To Microcontroller

Digital Modulation Signal Input

Figure 5. Low Noise Digital Modulation Circuit

The LIO can still be used to monitor the output current

when the LIS is modulated. The bandwidth of the LIO

signal is up to 9.17MHz, more than enough for monitoring

output current modulated by the LIS signal.

Monitoring the Output Current

The output current of the controller can be monitored by

measuring the voltage on the LIO pin. This feature is very

useful for micro-controller based system where the ADC is

available and monitoring the current in real time is

required. This pin provides a very low noise voltage signal

which is proportional to the output current:

×5(V).

For example, when the output signal equals to 2.5V, the

output current is 500mA.

The output impedance of this pin is 10

Ω and it can be used

to drive an ADC directly.

It can also be measured by a multimeter during debugging

process.

Figure 6 below shows the relations among LIS, LIMS and

Figure 6. LIO is Controlled by LIS and Clamped by LIMS

When the output current set by LIS is less than the current

with LIS linearly; when output current set by LIS exceeds

value set by the LIMS, see Figure 6.

Monitoring the Controller Internal Temperature

The controller internal temperature can be monitored by

measuring the TMPO pin voltage. The relationship

between the LMPO voltage and the temperature is:

)

(

479

.

3

8015

.

1

4182

.

2

10

04

.

1525

3

C

TMPO

T

°

−

+

+

−

=

(1)

where TMPO is the voltage on the TMPO pin.

This formula can be approximated by a linear equation:

)

(

31

.

90

7

.

192

C

TMPO

T

°

×

−

=

(2)

Within the most commonly used temperature range of

between 0

°C to 100°C, the maximum error occurs at about

1.5V, at which the temperature error between the

ATLS250MA106

ATLS500MA106