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ADP1660 flash LED driver application for VLED 4V/400mA

Hi all,

good day!

Our customer want to use 2S IR Laser diode (2V*2/400mA)

but we can't make sure HP LED driver (PMOS) spec..( I see the " LED current source headroom"  in the spec,  does it mean PMOS dropout voltage @load current ?)

so we want to know if we use 2S IR LD per ch, does it work normally?

thanks your help.

Regards,

Mars



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[edited by: Mars.Chang at 3:45 AM (GMT -4) on 15 Oct 2018]
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  • Hi Mars.Chang,

    Yes, the LED current source headroom is the drop at the PMOS. The VOUT voltage, based on the datasheet limits, can go up to 5V±425mV. This means that your worst case voltage at LED1 and LED2 would be 4.575V subtracted by the LED Current Source Headroom. The information in the datasheet is only typical but the load current condition on the datasheet is almost double your load current condition. If we use the typical datasheet value for the LED Current Source Headroom that means that the LED1 and LED2 voltage can still go up to 4.285V which should be enough for your forward voltage requirement of 2V.

    Hope this helps, and if you need anything else please don't hesitate to ask.

    Regards,
    Doc

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  • Hi Mars.Chang,

    Yes, the LED current source headroom is the drop at the PMOS. The VOUT voltage, based on the datasheet limits, can go up to 5V±425mV. This means that your worst case voltage at LED1 and LED2 would be 4.575V subtracted by the LED Current Source Headroom. The information in the datasheet is only typical but the load current condition on the datasheet is almost double your load current condition. If we use the typical datasheet value for the LED Current Source Headroom that means that the LED1 and LED2 voltage can still go up to 4.285V which should be enough for your forward voltage requirement of 2V.

    Hope this helps, and if you need anything else please don't hesitate to ask.

    Regards,
    Doc

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