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Low forward drop diode. Circuit malfunction Help required........

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Rajaneesh

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Hi All,

I have used PMEG1030EH (10 V, 3 A ultra low VF MEGA Schottky barrier rectifiers) in a charging circuit to block the DC supply.

Application : I have used this diode to block the DC supply from the Battery entering back to the input line through regulator during the external supply fails. At the same time, if external supply is present ,this diode will allow it to charge the battery. Now im facing a problem, if the external supply fails, the internal battery voltage is leaking through this diode and coming upto the input of the main voltage regulator and it also drives one of the LED in the input.

I checked the data sheet of this diode, it says there will be 2mA reverse current at 5V in reverse direction. Is it because of this ? (My internal battery voltage is 4.2V under fully charge condition)

When i replaced this diode with 1N4007 silicon diode, the circuit function properly and there is no issues. But i face more than 0.7v drop due to silicon diode. Is there any alternate germanium (low forward drop) diode which can solve this problem ?

Expecting a guidance in this subject plzzzzz.
 

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  • PMEG1030EH_EJ.pdf
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I don't think a 3A germanium diode (if one exists) would be suitable, as germanium diodes are more leaky than silicon diodes when reverse biassed.
 
hi Rajaneesh.:)

Look at the P MOSFET option in this pdf.

Will reply your PM later.

Eric
 

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  • Reverse_Batery_Protection.pdf
    149.6 KB · Views: 308
Hi Alec,

Thanks for ur reply... Is there any solution from any semiconductor companies..........? NXP claims its mean for DC blocking...i dun know wats wrong with this..
 
NXP claims its mean for DC blocking...i dun know wats wrong with this..
Well it does block DC, albeit imperfectly. 2mA is pretty small compared to 3A.:)
 
Is the LED being lit from the reverse current the problem? If so you might try just placing a resistor (perhaps 1k ohm or so) from the diode to ground to help bleed away the leakage current.
 
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