Schottky question - UK Vintage Radio Repair and Restoration Discussion Forum

ITAM805 · 30th Dec 2017, 5:03 pm

Hi all, my cheapo clone smart battery charger has died, amongst several shorted components I found an SR560 Schottky diode which measures a forward drop of 178mV. This is a suspiciously low drop, is it duff?

Many thanks.

jjl · 30th Dec 2017, 5:31 pm

That sounds believable for a Schottky diode, the nominal Vf is usually quoted as nominally around 200mV for small signal types, a bit higher for power types. The datasheet for your diode here

https://www.rcscomponents.kiev.ua/datasheets/sr560.pdf

quotes the maximum Vf as 700mV at 5A.

John

ITAM805 · 30th Dec 2017, 5:37 pm

Thanks John, Yes I noted the data sheet said 0.5 - 0.7V forward drop at 5A, but nowt about diode test conditions

Alistair D · 30th Dec 2017, 5:58 pm

I have an SR5100 5amp Schottky diode here that measures 190mV on the diode test function of my multimeter. As long as your diode measures high in the reverse direction I would say that it is a good un.

Al

ITAM805 · 30th Dec 2017, 6:02 pm

Thanks Al, yes it measures OL in reverse so I'll take that as a good component

kalee20 · 30th Dec 2017, 8:06 pm

It seems low to me too! But if it blocks in the reverse direction, then it must be OK!

Radio Wrangler · 31st Dec 2017, 12:27 pm

Big schottkys drop maybe 500mV when working in the on direction, but that can be at many amps. 190mV at the weedy current from the diode drop test of a multimeter is quite normal.

David

30th Dec 2017, 5:03 pm	#1
ITAM805 Nonode Join Date: Jul 2010 Location: Folkestone, Kent, UK. Posts: 2,172	Schottky question Hi all, my cheapo clone smart battery charger has died, amongst several shorted components I found an SR560 Schottky diode which measures a forward drop of 178mV. This is a suspiciously low drop, is it duff? Many thanks.

30th Dec 2017, 5:31 pm	#2
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Schottky question That sounds believable for a Schottky diode, the nominal Vf is usually quoted as nominally around 200mV for small signal types, a bit higher for power types. The datasheet for your diode here https://www.rcscomponents.kiev.ua/datasheets/sr560.pdf quotes the maximum Vf as 700mV at 5A. John

30th Dec 2017, 5:37 pm	#3
ITAM805 Nonode Join Date: Jul 2010 Location: Folkestone, Kent, UK. Posts: 2,172	Re: Schottky question Thanks John, Yes I noted the data sheet said 0.5 - 0.7V forward drop at 5A, but nowt about diode test conditions

30th Dec 2017, 5:58 pm	#4
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Schottky question I have an SR5100 5amp Schottky diode here that measures 190mV on the diode test function of my multimeter. As long as your diode measures high in the reverse direction I would say that it is a good un. Al __________________ I won't tell you how I discovered that.

30th Dec 2017, 6:02 pm	#5
ITAM805 Nonode Join Date: Jul 2010 Location: Folkestone, Kent, UK. Posts: 2,172	Re: Schottky question Thanks Al, yes it measures OL in reverse so I'll take that as a good component

30th Dec 2017, 8:06 pm	#6
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: Schottky question It seems low to me too! But if it blocks in the reverse direction, then it must be OK!

31st Dec 2017, 12:27 pm	#7
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Schottky question Big schottkys drop maybe 500mV when working in the on direction, but that can be at many amps. 190mV at the weedy current from the diode drop test of a multimeter is quite normal. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done