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LNK30x for DC/DC up to 50VDC converter - is possible ?

Posted by: RafW on Sat, 10/30/2021

Hi,

Is possible to use LNK302/304-306 family as switcher to convert input DC voltage up to 50V ( range 12...50V or only 35..50V) to DC about 5V? ( for PoE converter purpose )

Is any low voltage input limiter for this chips ?

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Submitted by PI-Hiro on Fri, 11/05/2021

Hello RafW,

On the datasheet of LNK302/304-306, there is a minimum drain pin supply voltage of 50V. This guarantees the operation of the power supply up to full load operation for the intended application. Although it may be possible for the power supply to operate at lower input voltages, it may only be possible for low loading conditions.

This is because as the input voltage decreases, there will be an increase in the duty cycle and this will be capped at DCmax as given in the datasheet. Once it reaches DCmax, the power supply output may not operate at full load condition. Another factor is that at start-up, the power supply may operate at the maximum duty cycle, but if it does not start-up properly within 50ms, the IC will enter auto-restart. 

You may try to build the power supply, but full load operation will only be guaranteed with a minimum drain pin supply voltage of 50V.

Thank you.

Regards,

PI-Hiro