ATLS1A103DEV1.0 datasheet(5/13 Pages) ANALOGTECHNOLOGIES

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Low Noise Constant Current Laser Controller

ATLS200MA103

Figure 7. Low Noise Digital Modulation Circuit

Note:

VVPS: the power supply voltage on VPS pin

VLDAMAX: the maximum output voltage of LDA pin

VLD: the forward voltage of the laser diode

VLDH: the highest forward voltage of the laser diode on the

modulation

VLDL: the lowest voltage of the laser diode on the modulation

VLIOH: the highest voltage of LIO pin

VLIOL: the lowest voltage of LIO pin

POLD: the optical output power of the laser diode

POLDH: the highest optical output power of the laser diode on

the modulation

ILD: the laser diode current

ILDH: the highest laser diode current on the modulation

ILDL: the lowest laser diode current on the modulation

Figure 8. Power Supply Voltage VVPS vs. LDA Pin Maximum

Voltage VLDAMAX

Maximum LDA Output Voltage vs. Power Supply Voltage

The maximum LDA pin output voltage is depending on the

power supply input voltage, VVPS. Their relationship is shown

in Figure 8. Therefore, it is recommended that:

VVPS

≥ VLDAMAX + 1V,

Where VLDAMAX is the laser diode’s maximum possible

forward voltage at the operation current.

To Avoid Output Current Distortions

The laser diode’s forward voltage and current has a non-linear

relationship shown in Figure 9.1 and 9.1. It can be seen that

when the current is low, the voltage is uncertain, it can be

between 0V to 1V or more. Thus, when setting the output

current to zero, the output voltage will oscillate between 0V

LDC

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