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2

Analog Technologies

ATLS4A217

High Voltage Constant Current 4A Laser Driver

Figure 2. Pin Names and Locations

Figure 2 is the top view of the ATLS4A217, which also

shows the pin names and locations. Its thickness is 4.5mm.

The pin functions and specifications are described in Table

1 below. Note that the metal case is internally connected to

ground.

Table 1.Pin Function Descriptions

Pin

#

Name

Type

Description

1

SYNO

Digital Output

Synchronization Output. This is a digital output signal with internal impedance of 100

Ω by

passed by 1.5MHz low pass filter. This output is triggered by the PWM output stage of this

laser driver and can be used to synchronize other switch mode electronics to avoid the beating

interference with their free-run frequencies if their free-run frequencies are close to 700kHz.

If the free-run frequency of other electronics is far away from 700kHz, no need to use this

pin.

2

TMO

Analog Output

Temperature Output pin. This pin indicates the controller temperature. The relationship

between the output voltage and the temperature is:

)

(

479

.

3

8015

.

1

4182

.

2

10

04

.

1525

3

C

V

T

TMO

°

−

+

+

−

=

or,

















−













+

−

=

4182

.

2

10

04

.

1525

479

.

3

8015

.

1

2

3

T

V

TMO

This formula can be approximated by a linear equation with

about 1% error between −40°C ~ 125°C:

)

(

1040

.

90

5576

.

192

C

V

T

×

−

=

or,

)

(

0111

.

0

1365

.

2

C

T

V

TMO

°

×

−

=

The maximum output current of the TMO pin is 1uA.

3

LPGD

Digital Output

Loop Good indication. When the laser driver's output current equals to the set-point current

value, and there is no short nor open circuit at the output, this pin is pulled up high by an

internal 3k

Ω resistor to an internal 4.5V power supply as shown in Figure 3; when the output

current is not equal to the set-point current, such as there is an open circuit at the output, or

the load has too high a resistance that even the output voltage reaches the power supply

voltage, the output current is still lower than the set-point value, this pin is pulled low by an

open drain MOSFET of which Rdson < 500

Ω. When outputting the low value, the sinking

capability is < 0.5V at 1mA.

4

SBDN

Analog/Digital

Input

Standby and Shutdown Control. This pin has 3 states: between 0V

∼ 0.4V, it shuts down the

entire laser driver; between 2.1V

∼ 2.4V, it sets the laser driver to standby mode; between

2.6V

∼ 15V, it sets the laser driver to operation mode. The input current on this pin is < 2µA.

(1)

(2)

(3)

(4)