Find an Schotcky diode for Input of power supply

Thread Starter

somaye2022

Joined Mar 23, 2022
99
Hi everyone,

First of all, thank you all for your helpful reply; it's kind of you!

Second, I am also looking for a Schottky diode for the power supply input in Attachment "D14".
I have found this RB068VWM-40TFTR (RB068VWM-40TFTR ROHM Semiconductor | Mouser Germany ); my question is how important is If - Forward Current, Ifsm - Forward Surge Current, If Ir - Reverse Current, and Vf - Forward Voltage to select a Schottky diode for this Input?

Iput of power supply.png
Best regards,
Somi
 

Choon Kwang

Joined Jun 6, 2022
9
The use of the schottky diode in your case seems to be for reverse polarity protection. Schottky diode is a simple solution to reverse polarity protection at the price of a forward drop voltage that you will need to pay. The Ir - Reverse Current should be able to withstand (or higher than) the max amount of current the power source provides.
 

Thread Starter

somaye2022

Joined Mar 23, 2022
99
The use of the Schottky diode, in your case seems to be for reverse polarity protection. Schottky diode is a simple solution to reverse polarity protection at the price of a forward drop voltage that you will need to pay. The Ir - Reverse Current should be able to withstand (or higher than) the max amount of current the power source provides.
Thank you for your reply,
Do you also have a better suggestion?
 

LowQCab

Joined Nov 6, 2012
2,171
Thank you for your reply,
Could you explain to me more about that?
.
You have not provided any Current "characterization" for your Load,
and why have You have chosen to use L-C-Filters.

And, what is "24-VDC", what is the "character" of your Power-Supply ?

Also, thanks for providing a Schematic, ( most people don't ),
but your Schematic is very hard to read and interpret and does not contain enough information.
.
.
.
 

Thread Starter

somaye2022

Joined Mar 23, 2022
99
.
You have not provided any Current "characterization" for your Load,
and why have You have chosen to use L-C-Filters.

And, what is "24-VDC", what is the "character" of your Power-Supply ?

Also, thanks for providing a Schematic ( most people don't ),
but your Schematic is very hard to read and interpret and does not contain enough information.
.
.
.
The circuit works with 24VDC and 12A current. LC-Filter is for Electromagnetic compatibility. Until now, it was of the Board another Schottky Diode, namely ONSEMI: MBRS240L-T3G. But it is not in stock until 27.09. Because of that, I must find an alternative for that?
 

LowQCab

Joined Nov 6, 2012
2,171
What is the "Inrush-Current" of your Load on start-up ?
Is ~12-Amps the "average" or "peak" Current ?
The Diode that You have chosen will definitely NOT work, ( it's rated for ~2-Amps ),
unless You are supplying us with the maximum Current-rating of your Power-Supply only, ( 20-Amps ? ) ,
and not the maximum-Current of the Load, which is the most important specification.

It would be easy to just go for extreme "over-kill" on the Diode-Ratings,
this will probably result in a lower operating Forward-Voltage, which would be a bonus.

"Not-in-Stock", in what country ?

The original MBRS240L-T3G is also a 2-Amp-rated Diode, ( Surface-Mount ),
did this Diode fail ?,
I would not be surprised because it is very difficult to get rid of HEAT with an SMD-Part,
and, at the maximum Current of ~2-Amps,
the Diode will have to dissipate around ~1-Watt of HEAT.
This amount of Heat may require an "add-on" Heat-Sink.
.
.
.
 

Thread Starter

somaye2022

Joined Mar 23, 2022
99
What is the "Inrush-Current" of your Load on start-up ?
Is ~12-Amps the "average" or "peak" Current ?
The Diode that You have chosen will definitely NOT work, ( it's rated for ~2-Amps ),
unless You are supplying us with the maximum Current-rating of your Power-Supply only, ( 20-Amps ? ) ,
and not the maximum-Current of the Load, which is the most important specification.

It would be easy to just go for extreme "over-kill" on the Diode-Ratings,
this will probably result in a lower operating Forward-Voltage, which would be a bonus.

"Not-in-Stock", in what country ?

The original MBRS240L-T3G is also a 2-Amp-rated Diode, ( Surface-Mount ),
did this Diode fail ?,
I would not be surprised because it is very difficult to get rid of HEAT with an SMD-Part,
and, at the maximum Current of ~2-Amps,
the Diode will have to dissipate around ~1-Watt of HEAT.
This amount of Heat may require an "add-on" Heat-Sink.
.
.
.
I appreciate your help,

I supply the Boards with 24 V and 12A of my Power-Supply. But 2 Amp for the Diode had worked very well until now.
In Germany is expected delivery time is about the end of September 27.09.2022 (too late for us). In comparison to the old one, is the new one "RB068VWM-40TFTR (RB068VWM-40TFTR ROHM Semiconductor | Mouser Germany )" fit for 2A? In my opinion, the big difference between these two diodes is Forward Surge Current which I thought that is supposed to be an Advantage when it changed from 25A to 30A, am I right?

with kind regards
 
Last edited:

Thread Starter

somaye2022

Joined Mar 23, 2022
99
Did the original Diode fail ?
.
.
.
No, we need more of that for production, I work in the development department and we redesign the Board because of new FPGA; because of that, I'm currently responsible for finding the right parts for the camera boards.
 

LowQCab

Joined Nov 6, 2012
2,171
It would appear that You are not the person who designed the Circuit,
but You are trying to find an alternative part because of supply difficulties.

If You can not characterize the Load in detail,
then no one in these forums can help You with answers as to
whether or not an alternate part will suit your needs,
especially in a production environment where
price, availability, and performance, must be weighed against each other.

All I can do is to say ...............
Do a Parametric-Search on your favorite supplier's website,
which will include the SMD package You are using, ( PMDE ),
and select a Diode rated for more than ~2-Amps, and rated for 30-Volts or more,
that is currently available in the quantities that You need for production.
.
.
.
 

Thread Starter

somaye2022

Joined Mar 23, 2022
99
It would appear that You are not the person who designed the Circuit,
but You are trying to find an alternative part because of supply difficulties.

If You can not characterize the Load in detail,
then no one in these forums can help You with answers as to
whether or not an alternate part will suit your needs,
especially in a production environment where
price, availability, and performance, must be weighed against each other.

All I can do is to say ...............
Do a Parametric-Search on your favorite supplier's website,
which will include the SMD package You are using, ( PMDE ),
and select a Diode rated for more than ~2-Amps, and rated for 30-Volts or more,
that is currently available in the quantities that You need for production.
.
.
.
I appreciate your help,
Honestly, I started my job as a hardware developer three months ago after graduating with my Master of Science in electronics. I have had some small circuits to develop and optimize. My task will go further in the developing way when I know the Boards, devices, and every part of that deeply; because of that, I try to understand the existing design and want to ask a question in this forum to know a lot of things and point of views of the experienced people to develop myself and not just find a part!
Kind regards
 
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